PROCEEDINGS OP SOCIETIES.

DUBLIN MICEOSCOPICAL CLUB.

11th January, 1878.On the Development of the Siphons in Polysiphonia.—Dr. B.

Perceval "Wright exhibited Home mounted specimens presentingthe form of apical growth so characteristically described byNageli in the ' Zeitschrift fur wiss. Botanik,' 1836, and showingin addition some new facts (as he believed) in the developmentand growth of the so-called siphons in Polysiphonia. Thespecies selected was one with four siphons, representing thesubgenus Oligosiphonia. Such a species would be described aahaving a" frond consisting of four tubes radiating round a centralcell, and generally containing endochrome" (Harvey), or, as byAgardh, in some detail, as " Cellulre istse perieentrales, quassiphones vocant, sunt endochroraate colorate repletse, parietibushyalinis crassis, polystromaticis invicem et a cellulis articulorumproximorum separate." But all such-like descriptions appearedto Dr. Wright to be based on a misconception of the structure tobe seen when the living plant is carefully studied, and whenquite fresh specimens are submitted to the action of re-agents.It then become s pretty evident that the growing filament inPolyBiphonia is in reality one continuous cell bounded on allsides by its own well-marked cell-wall, that below its growingpoint, below the layer of homogeneous protoplasm, and beloweven that so-called granular protoplasm of Nageli, there exists aprotoplasm, which has, as it were, taken up its maximum quan-tity of water of organisation, has become a viscid, almost sensi-tive substance, capable of forming out of itself chlorophyll andstarch-granules, and, on occasions, exhibiting, in some allied forms,all the characteristic movements of animal pseudopodia. In thislayer the siphons originate. In the species exhibited the processwas—(1) a thin lozenge-Bhaped plate of the protoplasm becamedetached all but in five parts, where the thread-like continua-tions kept the little lozenge of protoplasm from falling awayfrom the upper portion ; (2) this lozenge increased greatly inthickness,and after a certain thickness had been attained,it dividedaBunder into a central portion and four equi-dimensioned peri-pheral portions ; each of these latter still attached to the centralportion by prolongations from the centre of their long diameter

346 PROCEEDINGS OF SOCIETIES.

and each of the free masses, it will be borne in mind, is alsoattached by similar prolongations to the five masses already belowthem, and will be equally attached to the five masses that will beformed above them. When these masses, which are the '' siphons "of the algologist, reach adult age, a delicate cellulose membraneforms around each, and between these and the common investingcell-wall there is sometimes a well-marked interval, which is insome species filled up by cellules. No true articulation at thisstage exists in the stem ; it only occurs later in life, and in amanner seemingly as yet undescribed.

Structure of Spines of Toxopneustes variegatus, Lamk.—Mr.Mackintosh exhibited a cross section of the spine of Toxopneustesvariegatus, Lamk., which showed two cycles of solid wedges,the inner very small, the outer much larger, globular in contour,and connected to each other by single short bars perforated witha few delicate tubes.

Magnetic Particles occurring in Arctic Ire-dust.—Dr. Moss,R.N... exhibited a sample of Arctic Ice-dust, and showed inter-miDgied magnetic particles under the microscope, calling atten-tion to their movement under a magnet caused to move aboutunder the stage.

An Oscillatoria from Australian Seas, occurring in large quan-tities.—Mr. Archer exhibited examples of an alga forwarded byProfessor Thiselton Dyer, an Oscillatoria from the surface of theAustralian Seas, often forming large masses and thrown ashore.Locally, this was popularly called Whale-Spawn, and its naturemisunderstood, being accounted there as somehow a kind ofslough or exuvium from certain polypes. Whether originallycolourless or whether by drying it had become bleached was un-certain. The cells were unequal in Bize. In the mass this pro-duction is described as giving off a very foul smell; this however,more than probably, may be only when it is undergoing decom-position in the sun on the beach. Perhaps the most remarkablecircumstance connected with it was the vast quantity in which,at certain seasons, it would appear to occur.

Polariscopic aspect of Artificial Gems.—Mr. Grrubb showedthe polariscopic appearance of certain of the artificial gems(sapphire, &c.) now being manufactured by M. Feble of Paris,in which respect they are not to distinguished from genuinestones.

" Japanese Isinglass."—Mr. Draper showed sections of the so-called Japanese Isinglass, and stated he had arrived at tlie sameconclusion as Professor Mr. Nab, that this was in reality ^oineform of starch.

Navicula Hfossiana, n.s., O.'M., exhibited.—Rev. E. O'Mearashowed a slide from material dredged from a depth of sevenfathoms ia Discovery Bay 81° 43' N., for which he was indebtedto the kindness of Dr. Moss, E.N., late of H.M.S. "Alert."Amongst the forms contained was one belonging to the genusNavicula, which he considered not hitherto named, and proposed

DUBLIN MICROSCOPICAL CLUB. 3 4 7

to designate N. Mossiana as follows: Valve broadly elliptical,length 0027", breadth '0018"; median line well-marked, lyingin a narrow, unstriate, linear space, with a wide quadrangularexpension around the central nodule ; striae distinct, close,punctate, slightly radiate in the middle, more and more decidedlyradiate towards the ends; towards the middle of the valve thelines of puncta are interrupted, 80 as to form on either side of themedian line two or three distinct longitudinal bands, nearlyparallel to the median free space. Schmidt has figured withoutnames some forms which strongly resemble the present, ' Atlasder Diat.,' t. vi, figg. 35, 36, 39.

27th February, 1878.A. New Mineral from C'arnmoney Sill, near Belfast, exhibited.

—Professor Hull, IM&.S., exhibited a thin section of the OlivineBasalt of Carumoney Hill, near Belfast, containing a mineralconsidered by Mr. E. T. Hardman, F.C.S., who has analysed it,to be new. The mineral is black, glossy, and gives an olive-brown streak; hardness 2'5, sp. gr. 1609—1700. It occurs asa material filling cells and cavities in the original rock and oftenBurrounding the crystals of felspar, olivine and augite. It is ina gelatinous, uncrystalline condition, and does not polarize underthe microscope ; with a low power it is seen to be of a chocolateor yellowish-brown colour, passing into black in the thicker por-tions of the slice. No special structure is observable, but with ahigh power faint, wavy lines,like those of stalg' mite or chalcedony,were observed, giving evidence of a formation from aqueous solu-tions. The author had no doubt, both from the; characters of thiamineral under the microscope and from the chmical analysis ofMr. Hardman, that it was a secondary mineral, derived fromaqueous solution after the rock had consolidated from the crys-talline state.

The following is the analysis:Silica . . . . 39352Alumina . . . . 10-452Peroxide of iron . . . 20769Protoxide „ . . . 3 6 9 9

„ manganese . . trace.Calcium oxide . . . 4-484Magnesium „ 7'474Water (confined) . . . 13-618Zinc oxide . . . . trace.Organic matter .. . . „

99848per cent.A. New Variety of Stysanus stemonitis, exhibited.—Mr. Pirn

showed a remarkable mould which grew on a bamboo-stake inUis hothouse. It bore no resemblance to any mould figured in

348 PROCEEDINGS 01' SOCIETIES.

either Cooke or Corda, except Stysanus stemonitis, Corda, fromwhich it differed in the fact that the stem, instead of being simpleand surmounted by a cylindrical head of concatenated spores,waa divided into numerous branches, each terminated by a headof spores, the way in which the threads of the stem passed intothe branches strongly reminding one of the divisions of sometendons. A specimen was subsequently shown to Mr. Vine, andby him to Mr. Phillips, of Shrewsbury, and both concur in con-Bidering it a branched form of the species named. As its claimto specific rank is doubtful, Mr. Pim would suggest that it becalled Stysanus stemonitis, Corda, var. ramosa, Pim.

A new Micrasteriasfrom Scotland,forwarded by Mr. J. P.Bisset,Banchory.—Mr. Archer exhibited a new Micrasterias, kindlysent to him from Scotland, by Mr. J. P. Bisset of Banchory, nearAberdeen, and collected by that gentleman on the Dee-side. Thispresented denticulations like those of M. denticulata, with someof the contour of M. angulosa, but seemed well distinguished bythe possession, oa each front surface, near the base of each semi-cell, of a curved series of circular groups of bead-like mark-ings, of which the central group was the largest, the externalones being the smallest. These seemed to Mr. Archer to becomposed of leaflike prominences, and the groups he supposed,were it possible to view them laterally, would be seeu to standout as crown-like elevations, somewhat comparable to those, say,jf Xanthidium armatum, but most likely not by any means soprominently—that is to say, the component bead-like markingsdid not appear as dots or even granules, but, as he said, thin leaf-like projections. Mr. Bisset referred to other " markings," but inthe specimen, owing probably to the presence of the cell-con-tents, no others could be noticed. These examples formed aportion of a set of two or three slides of species carefully selectedand exquisitely mounted by Mr. Bisset—one contained six speciesof Micrasterias, represented by one example of each, -M. rotata,M. denticulata, M. truncata, M. papillifera, M. angulosa, and thenew species.

Section of Spine of Mespilia globulus, exhibited.—Mr. Mackin-tosh exhibited a cross section of the spine of Mespilia globulus,which had been kindly sent him by Dr. Giinther, F.B.S. Thegreater portion of the spine was composed of reticulations withthick trabecules, the periphery being formed of a single row ofsolid wedges, whose form was almost that of an equilateraltriangle.

Peculiar condition of "Rivularia.—Dr. E. Perceval Wright ex-hibited sections from examples of Rivularia, showing a peculi-arity in certain of the component filaments, consisting in the factthat these presented a clavate expansion in place of the ordinarytapering, inside which expansion the cells formed indefinitegroups, not linear series. Possibly, in function these might becomparable to the mamillate branches of such forms as Stigo-nema mamillosum, in which, however, the cells remain in single

DUBLIN MICROSCOPICAL CLUB. 3 4 9

series, though indefinitely scattered in the stems, and, in Rivu-laria, like them destined to become removed and serve to thevegetative propagation of the plant. Such a mode of vegetativegrowth does not appear to have been noticed in Rivularia.

Some Arctic Diatoms, amongst which Biddulphia Balcena,which appears rather to he a Trir.eratium.—Rev. E. O'Mearashowed a slide containing Diatoms, collected in ^Franklin Bay byMajor Fielden, R.A., Naturalist to the Arctic Expedition. Thecollection is a most valuable one, containing numerous rarespecies, amongst which are to be found Coscinodiseus punctatus,Greg.; Synedra JLamskatica, O'M.; Grammatophora aretica, Cleve;Rhabdonema Torellii, Cleve; Pleurosigma longum, Cleve ; Thai-lasiosira Jtfordshioldii, Cleve ; Shoiconema bollinana, Grunow ;Triceratium arcticum, Brightwell; Biddulphia Balcena, Bright-well. To this last Mr. O'Meara directed special attention, andexpressed his opinion that it would be more properly included inthe genus Triceratium. Except as regards its somewhat rhom-boid outline the characters closely resembled Triceratium arcti-cum, with which it was not unfrequently associated.

21st March, 1878.

Verrick's \th.—Mr. Richardson drew special attention to theexcellence of this objective. It was the power (about th) suppliedby Verick with his low priced stand, and defined so well that he,Mr. Richardson, preferred it for demonstrating most sections toglasses of some other makers of about the same power in hispossession, each of which cost considerably more than Verick'sstand and its two objectives. Moreover, the glass without anyspecial arrangement therefor, acted equally well whether as a dryor as an immersion lens.

Structure of Spine of JSchinus acutus, Lamk.—Mr. Mackintoshexhibited a cross section of the spine of JEchinus acutus, Lamk.The specimen from which the spine was taken was dredged offthe coast of Toughal by the late Dr. Ball, who described itunder the name of Echinus Flemingii, but A. Agassiz, ('Reviewof the Echini,' 1872), has placed it as a variety only of Lamarck'solder species. The example was presented by Dr. Ball to theMuseum of Trinity College, Dublin, and Mr. Mackintosh wasindebted to the kindness of Professor Maealister, the presentDirector, for the opportunity of examining the structure of thespines. They present in cross-section the usual axis of reticulartissue surrounded by four cycles of solid wedges, separated fromeach other by spokes of trabecular tissue. The cycles might bedescribed as being produced by the constriction at intervals ofa single elongated wedge, such as is seen in the Bpine of theallied _E. esculentus, Linn., a section of which was shown for sakeof contrast.

Lafoea pocillum, exhibited.—Mr. Grant showed Lafoea pocillum,one of the Campanularians, of considerable rarity, Hiucks, in his

3 5 0 PROCEEDINGS OF SOCIETIES.

wort on the " Hydroid " Zoophytes, stating that he had met withit only at Oban. Mr. Grant met with it at Howth. It is minute,with short beaded stem and long tubular capsule.

Docidium nodosum, American example, exhibited.—Mr. Archershowed an example of Docidum nodosum occurring in a smallcollection labelled as made at New Jersey, in America, and forsome years lying in the Herbarium of Trinity College, and forthe examination of which Mr. Archer was indebted to ProfessorPerceval Wright. For a long time this appeared to be a purelyAmerican species, but Mr. Archer had some time ago made itsacquaintance at Comemara, but he had seen two examples only.It had since been gathered in Sweden. It is an unmistakable,fine, bold, and handsome species.

Cephalic Armature of Clio borealis, exhibited.—Dr. Mossshowed the cephalic armature of Clio borealis, and some beautifuloriginal drawings in illustration, showing also the entire animalas it appears in the act of swimming.• New Species of Craspedodiscus, C. Febigeri, exhibited.—Rev.Eugene O'Meara exhibited a new species of Craspedodiscus fromthe Nottingham deposit. The slide was sent by Mr. Ifebiger ofWilmington, U.S., through Mr. Habenshaw of New York. Mr.Febiger doubtfully assigns the form to the genus Craspi dodiscus,but close examination removes all doubt as to its proper place.Like Craspedodiscus elegans, this species possesses a centralrosette of eight elongated areoles. The central part of the discis not so distant from, the border as in some other species, yetsufficiently deSned to constitute in form a genuine Craspedo-discus. The areoles are hexagonal, radiately arranged, somewhatsmaller in the central portion than in the marginal. The mar-ginal portion is somewhat broader than the radius of the central.Tbe form is large, being in diameter O'l" Mr. O'Meara pro-posed to name this form Craspedodiscus Febigeri.

On the Development of the Tetraspores in Polysiphonia.—Dr.E. Perceval Wright exhibited some recent preparations showingthe development of the tetraspores in Polysipkonia nigreseens.He was not aware of any researches on this subject, but theseries of specimens would clearly show that the mass of proto-plasm which in time developed into the cell with the tetraapores,took its origin from the base of the central siphon, first present-ing the form of an oval mass, then becoming stalked; it nextgreatly increased in size, and in doing so pressed out the externalrows of sephons which surrounded it, giving thus to the tetra-Bporic ramule its well-known irregular form of outline; after a littlethe central portion of the cell contents divided into the fourportions forming the tetraspores. The stalk, though still plainlyvisible with a sufficient power, was very slender in comparisonwith the mass it bore.

SL1B1. JWBL Hate XH.

JOURNAL OF MICROSCOPICAL SCIENCE.

EXPLANATIONS OF PLATE XII—XV.Illustrating C. O. Whitman's paper on " The Embryology

of Clepsine."(All the figures are outlined with the camera lucida.)

a, 6, c. Permanent blastomeres. or. Anal ring of dorsal blood-vessel.

segmental organ. Ent. Entoderm. Ep. Epidermis, f.pn. Female pro-nucleus, f.pnl. Female promicleolus. gb. Germ-bands, ia. Internal ori-fice of segmeiital organ, id. Diverticula of intestine, t. Intestine, m.Mesoderm. m.Pn. Male pronucleus. m.Pnl. Male pronucleolus. Med.SMedian sinus, m. Marginal sinus. «. Nerve-cells, o. (Esophagus. oa>Pharyngeal atrium, o.c. Pharyngeal clefts. P. Pharynx. Pa. Polar areaof amphiast.er. Pa. Pharyngeal aperture (mouth, figs. 37—49). Pb.Pliaryngeal branch. Pf. Polar figure. Pg. Polar globules. Pgr. Primi-tive groove. Pr. Polar riug (upper). Pr'. Polar ring (lower). Pi. Pro-toplasm-zones, s. Segment-cells. Seg.c. Segmentation cavity. Seg.O.Segmental organ. Sep. Septa. S O.O. Suboesophageal ganglia. SI. Sto-mach, l.bg. Terminal body-ganglia, vt. Ventral trunk. * §• xy. Meso-blasts. xl—if*. Neuroblasts. z. Problematic cells.

PLATE XII.(Figs. 1—55 magnified about 25 diameters.)

FIGS. 1—7-—A peristaltic constriction, resembling the first cleavageconstriction, pusses from the middle of the egg (fig. 2) towards the polarfigure {Pf), and is followed by the extrusion of the first polar globule (fig.7, Pg). Time from fiir. I to fig. 7, 10—15 min.

FIG. 8.—Form of egg after appearance of the second pol. globule, (1 h.2a min. after deposit.)

FIG. 9.—First ring appears around the shaded area of fig. 8. (1 h. 30min.)

FIG. 10.—Second ring (Pr') appears, and at about the same time ring-rays from the upper riug. (1 h. 35 min.)

FIG. 11.—The calotte much reduced (col). The lower ring-substancecovers the aboral pole in the form of a disc. Kays of the ring-substanceseen at both poles. (

FIG. 12.—Just before the appearance of (he cleavage furrow. Calottehas approached one Bide of the ring, and the rays have nearly disappeared.(2 h. 45 min.)

FIGS. 13 and 14.—Two views of the same egg as the cleavage begins.Pr is reduced to a mere point. Pr has assumed a crescentic shape.(3 h.)

FIG. 15.—The first meridional cleavage completed. The cleavage wallsclose up sooner on the upper than on the lower pole. (3 li. 30 min.)

FIG. 16.—Thirty minutes later. Sees from above. Pr begins to dis-appear.

EXPLANATION OF PLATE \ll—Continued.

PIG. 17.—The second meridional division begins to cut the larger of thetwo spheres, passing from the centre outwards. (5 h.)

FIG. 18.—Ten minutes later the cleavage begins on the smaller sphere,advancing in the opposite direction.

FIG. 19.—First two meridional divisions completed. (5 h. 30min.)FIG. 20.—The first ectoblast is in process of formation from the upper

pole of the largest blastomere (x). (6 h. 30 min.)FIG. 21.—The second ectoblast in process of formation from the blasto-

mere (6). The first ectoblast has been pushed to the left into the blasto-mere (a). (7 h.)

FIG. 22.—The third and fourth ectoblasts are forming simultaneouslyfrom a and c. (7 h. 30 mia.)

FIG. 23.—The formation of the four primary ectoblasts is completed, andx begins to divide. (8 h. 30 min.)

FIG. 24.—Thirty minutes later, from below. The division of x is welladvanced. (9 h.)

FIG. 25.—The egg is seen from below. The division of x into x' andx has been completed. (12 h.)

FIG. 26.—The same from above. Three or four cells have been added tothe primary ectoblasts from a and b.

FIG. 27.—Two hours later, from below, x is in process of division.(14 h.)

FIG. 28.—Thirty minutes later. (14 h. 30 min.)FIG: 29.—Seen from below. The division of the original blastomere (x)

(fig. 22) into the two mesoblasts (a: and xy), and the primary neuroblast (x )is accomplished. (14 h. 45 min.)

FIG. 30.—Seen from above. Ten to twelve cells have been added to thefour ectoblasts. x' begins to divide, the plane of cleavage passiug fromabove downward. (21 h.)

FIG. 31.—The four primary ectoblasts are completely encircled with cellsderived from a, b, and c. The division of x> into a;2 and x" is completed.(24 h.)

FIG. 32.—The same from below.FIG. 33.—The two cells (x2) are in process of cleavage. (24 h. 15 min.)]?io. 34.—The division of the two cells (x3) into the four cells (a:3) is com-

plete. The four primary ectoblasts have divided each into four parts.(24 h. 30 min.)

FIG. 35.—The two median cells (a:3) have pushed each other apart bynipple-like protrusions of their contiguous faces. Ou the left, just above(xy), are seen four cells in a row. They have been produced from the upperpole of the mesoblast (xy). (26 h. 30 min.)

FIG. 36.—The nipple-like protrusions have been constricted off as twosmall median cells (a;4). The mesoblast (a;), which occupies the lower pole infig. 29, has changed its position, passing backward and upward, followedby the ventral blastomere (c). It now lies just under the two cells (x4).This egg is seen from the left side. (26 h. 40 min.)

FIG. 37.—The two cells x* have broken up into smaller cells. The twomedian cells (a ) have produced the two cells (a?), and the two outer cells(a:3) have produced a:6. This completes two symmetrically placed groups ofneuroblasts, each group consisting of four cells (x*, x*, x6, a;3). The line ofmesoblastic cells produced by xy is still to be seen. The nuclei of a, b, andc have each divided into three or four parts, which are now seen in thesurface of the blastomeres. These free nuclei are spoken of in the text as" entoplasts." The mesoblast (x) has completely disappeared, being coveredby the posterior ends of a, b, and c. xy has also sunk deeply into a, but isstill plain to be seen. (28 h. 30 min.)

EIG. 38.—The two neuroblasts x* are covered with ectodennic cells. The

EXPLANATION OF PLATE XII— Continued.

germ-bands appear as two thickened lateral margins of the germinal disc.The place of the future mouth {pa) is seea in the centre of the cephalicmass; this point marks nearly the centre of the four primary ectoblasts.The pharyngeal clefts {pc) are marked by slight depressions at the line ofjunction of the germ-bands with the cephalic portion. (36 h.)

FIG. 39.—The same from below. The entoplasts have increased innumber.

FIG. 40.—Only the thickened margins of the germinal disc are repre-sented. The four superficial lines of cells produced by the neuroblasts givetbe bands a striated appearance. The fore ends of the bauds rise above thelevel of the cephalic portion, as is plainly seen when the egg is tilted. Thepharyngeal clefts (oc) are now nearly parallel with the linear depressionleading backward from the mouth (Pa). (42 h.)

FIG. 41.—The anterior ends of the germ-bands are already in contact,and the pharyngeal clefts are nearly at right angles to the postoral depres-sion, which is seen to be continuous with the primitive groove {p.gr).(48 h.)

EIG. 42.—The same, tilted on the hind end, to show that the ventralblastomere (c) is being driven up between the lateral blastomeres (a, b).

FIG. 43.—The same seen from behind. The entoplasts, which are notrepresented in the following figures, are quite numerous, and scattered overthe entire surface of a, b, and c.

FIG. 44.—Seen from behind. The germ-bands are about two thirdsclosed. The ventral blastomere (e) is now wider on the dorsal than on theventral side. (60 h.)

FIG. 45.—The same, seen from before. The metameric formation alreadybegun.

FIG. 46.—The germ-bands most closed. The pharyngeal clefts haveencircled the pharyngeal portion. The ganglionic formation is quite dis-tinct. A few hours before hatching. (72 h.)

FIG. 47.—The same, xy is seen as a dark area in the right side.FIG. 48.—The neuroblasts, which are much reduced in size, form a semi-

circle around the posterior ends of the fully closed bands. The two meso-blasts appear as ill-defined dark spots, lying near the surface of a and c.(One day old.)

FIG. 49.—The same, seen in profile. The segment-cells are seen betweeneach met.amere.

FIG. 50.—The pharynx protrudes a little, xy is less distinct. Thesepta are lengthening towards the dorsal side. The boundary lines of a, b,and c have disappeared. (3 days old.)

FIG. 51.—The same, from the ventral side.FIG. 52.—The dorsal side is still shorter than the ventral. The three

main divisions of the digestive tract with their cieca are now recognisable.The septa have not yet reached tbe dorsal side. (6 days old.)

FIG. 53.—Of the same age, but farther advanced.EIG. 54.—Also of the same age, but still farther advanced. The dorsal

and ventral sides are of about equal length.FIG. 55.—The worm has nearly attained its definitive form. The eyes

appear about this time as orange-coloured spots. (7 days old.)

PLATE XIII.FIG. 56. -Circulatory apparatus, digestive tract, and one of the segmental

organs. Magnified circa 50 diam. (14 days old.)FIG. 57.—A transverse section of the egg-string, showing the central

nucleated protoplasm (rhachis) and the peripheral layer of primitive egg-cells. Magnified 440 diam.

FIG. 58.—A longitudinal, optical section of the egg-string, a, b, c, andd = successive stages in the growth of the egg-cell. The rhachis is heremuch larger comparatively than in fig. 57. Magnified 160 diam.

FIG. 59.—A portion of the egg-string at a time when the eggs have cometo lie externally to it. Magnified 50 diam.

FIG. 60.—Three vesicnlse genninativse. a represents the vesicle at thetime the egg is liberated from the string, 6 is the vesicle of the full-grownegg, and c is probably an incipient relicular stage. Magnified 160 diam.

FIG. 61.—Nucleus corresponding nearly with the stage represented infig. 58. The homogeneous nucleolus lies in the centre of the reticulum.Magnified 4-AO diam.

FIG. 62.—Section of a fresh-laid egg, showing the archiamphiaster. Onlya part of the section is represented. Magnified 160 diam.

FIG. 63.—The second polar globule is in process of elimination. Magni-fied 160 diam.

FIG. 64.—One pole of the amphiaster in fig. 62 more highly magnified.(440 diam.).

FIG. 65.—A. Section of the egg just after the formation of the polarglobules. The male (wi.Ps) and female (f.Pn) prouuclei are present.Magnified 50 diam.

B. The polar globules highly magnified. (Zeiss J. and the cameranach Oberhauser.)

FIG. 66.—C is a section of the egg at the time the first polar ring beginsto form. The pronuclei are approaching each other. In the female pro-nueleus two pronucleoli are seen in close contact. The same are morehighly magnified in D. The. male prouucleus (magnified 160 diam. in E)contains only one nucleolus. F represents the united pronuclei.

FIG. 67.—G is a section of the egg just after the union of the pronuclei.The path of the female pronucleus is indicated by the shaded line. Mag-nified 50 diam. H and I are two primary cleavage-nuclei. Magnified 160diam.

PLATE XIV.FIG. 68.—K is a section of the egg thirty minutes after the appearance

of the first polar ring. The second ring already covers the lower pole. Lrepresents the cleavage-nucleus of another section. Magnified 160 diam.N = the three pronucleoli.

FIGS. 69, 70, and 71 (O) represent sections of the egg forty-five minutes,sixty minutes, and sixty minutes respectively after the appearance of thefirst polar ring, showing the concentration of the rings. In fig. 71 (O) thenucleus is spindle-shaped, but the nucleoli are still unchanged. P is anothernucleus of the same date, magnified 160 diam.

FIG. 72 —The nucleus has assumed the amphiastral form, and the ring-substance has plunged deeper into the egg. This section bears the samedate as figs. 70 and 71, but is evidently farther advanced. Magnified 50diam.

FIG. 73.—A little farther advanced than fig. 72, although of the samedate. Magnified 50 diam.

FIG. 74.—A moment before the first cleavage begins.

cnl/"• n, 08.

JoumMicr. Science N. S.V

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JdiiNi. Micr Science X S. Vol.XVIII. Plate XV.

EXPLANATION OF PLATE XIV—continued.

FIG. 75-—The cleavage has begun. The length of the amphiaster liasreadied its maximum.

FIG. 76.—First cleavage completed, but the two nuclei are still connectedby a slender band of nucleoplasm.

FIG. 76 B,.—One of the two nuclei in fig. 62, magnified 160 diam.FIG. 77.—A section of the upper polar ring, taken about 1 mm. under

the surface. The more darkly shaded ring arouud the base of the calotteis seldom seen. Magnified 50 diam.

FIG. 78.—One pole of the amphiaster (fig. 73), magnified 440 diam.PIG. 79.—A transverse section through the middle of an egg arrived at

stage 26, PI. XII. T represents the nucleus of one of the ecloblasts atabout the same date, magnified 440 diam.

FIG. 80.—A horizontal section of stage 36, PI. XII, taken just below thegerminal disc.

FIG. 81.—A transverse section of stage 37, PI. XII, taken just behindthe germinal disc, to show the positions of the mesoblasts (x and xy). Cellsare seen leading from the nuclear poles of the mesoblasts up to the germi-nal disc.

FIG. 82.—A longitudinal section of the same date, which passes throughthe middle of the left mesoblasl (x).

FIG. 83.—A horizontal section of the same date, below the germinal disc.The nuclei lie near the surface of the blastomeres.

FIG. 84.—A transverse section just in front of the neuroblasts (stage 41,PI. XII). A line of cells leads from each inesoblast to the germ-baud ofthe corresponding side.

FIG. 85.—A transverse section at a little later date.FIG. 86.—A median transverse section (stage 44, PI. XII). x and xy

have changed their positions with reference to each other in consequence ofthe invagination. Compare with fig. 84.

FIG. 87-—A horizontal section (stage 43, PI. XII). In the anterior part(lower part of the figure) the germ-bauds have united, but in the posteriorpart they are still unclosed.

FIG. 88.—A median transverse section at the time of hatching, showingthe nerve-cells («) and a pair of segment-cells {s). Magnified 160 diam.

FIG. 89.—A similar section two days later.

PLATE XV.FIG. 90.—A sagittal section, showing the origin of the nerve-cells and

the segment-cells. Just hatched. Zeiss. A, A. and camera.FIG. 91.—Embryo freed from the yolk, showing the number of body-

segments and the position of the segment-cells (s). (2£ days old.) Mag-nified 50 diam.

FIG. 92.—A segmental organ and one of the segment-cells 3£ days afterexclusion. Magnified 440 diam.

FIG. 93.—A sagittal section (constructed from two successive sections)showing the condition of the entoderm eight days after exclusion. Magni-fied abont 25 diam.

FIG. 01.—A portion of a horizontal section, one day later. The euto-dmuio cells are arranged iu a single compact layer. MaguiGed 160 diam.

FIG. 95.—A portion of fig. 93 magnified 160 diam. The entodermiccells are loosely arranged in the periphery of the yolk.

FIG. 96.—A horizontal section, passing near the middle of the pharynx.About three days old. Magnified 50 diam.

Journ. Micr. Science N.S.i^i XVI

• n

JOURNAL OP MICROSCOPICAL SCIENCE.

EXPLANATION OF PLATE XVI,

Illustrating Dr. Klein's paper, " Observations on theStructure of Cells and Nuclei."

FIGURES 1—12 (incl.) refer to preparations of stomach, 13—23 tothose of mesentery of newt. For method of preparing see text. Allfigures are represented as seen on Hartnack's small stand with eye-pieceIII, and Zeiss's objective F, except 17 e, which is drawn with Hartnack'sNo. 10 Immersion.

FIGS. 1 and 2 represent goblet-cells ; the intranuclear network is wellshown, and also the fibrils passing from this into the upper and lowerpart of the cell.

FIG. 3, a, b, and c.—The intranuclear network separated from themembrane of the nucleus.

FIG. 4.—A goblet-cell (like that of 1 and 2) as seen obliquely fromabove, showing the intracellular network.

FIG. 5.—The intracellular network looked at vertically from above.FIG. 6.—Two isolated nuclei showing the intranuclear network ; this

has shrunk to a considerable extent.FIG. 7.—A gland-cell, showing the dense network of fine fibrils

of the cell-substance; the nucleus has escaped, but there are still left afew fibrils, probably connecting the two networks, viz. the intranuclearand the intracellular.

FIG. 8.—An isolated nucleus of a gland-cell; the wall of the nucleusis broken at one place and the intranuclear fibrils are seen passingoutwards.

FIG. 9.—A connective-tissue corpuscle—endothelial plate—seen inprofile; both the intracellular fibrils and those of the intranuclearnetwork are well shown.

FIG. 10.—A similar cell seen from its broad surface.FIG. 11.—Portion of a cell; the intranuclear network shrunk.FIG. 12.—Two epithelial cells; the intracellular fibrils are well shown.

The top of both cells is seen in an oblique direction, and the network offibrils is therefore brought into view. Preparation treated withMiiller's fluid and then with mixture of chromic acid and spirit; seetext.

FIGS. 13, 14, 15.—Isolated endothelial plates of surface of mesentery.The intracellular and intranuclear networks of fibrils are well shown.

FIG. 16.—A capillary blood-vessel; the two upper nuclei are seen fromtheir broad side, the two lower in profile. They all show the network offibrils. In the lower portion of the wall of the vessel an imperfectnetwork of fibrils may be perceived.

EXPLANATION OF PLATE XVI— Continued.

FIG. 17, o and b.—Two unstriped muscle-fibres. The intranuclearnetwork of fibrils is well seen; these are in connection with fibrils ofthe substance of the muscle-fibre; there are seen numerous transversemarkings along almost the whole length of the muscle-fibre. That thesetransverse markings, corresponding to rings which constitute the corticalpart, »'. e. the sheath, is well shown in c, d, and e.

FIG. 18.—A non-medullated nerve-fibre of mesentery of newt; thenerve-fibre has a delicate sheath, the nuclei of which contain a distinctnetwork of fibrils.

FIG. 19.—Two connective-tissue corpuscles seen side-ways. Thenucleus contains a network of fibrils, in connection with that of thecell-substance.

FIG. 20 and 21.— Two migratory cells; 20, a common pale one, 21, acoarsely granular one. Their nucleus shows the network of fibrilsvery well.

FIG. 22.—A caecal dilatation of a lymphatic vessel of the same mem-brane, showing the nuclei of the endothelial cells forming the wall ofthe lymphatic, and also nuclei of lymph-corpuscles.

PIG. 23. o and c.—Two connective-tissue corpuscles; the distinctionbetween ' ground-plate' and ' fibrillar substance' is well shown ; the' fibrillar substance' is in connection with the intranuclear fibrils.

b, a nucleated plate ensheathing a minute non-medullated nerve-fibre.The intranuclear network is seen in connection with the processes andfibrils of the connective-tissue corpuscle c.