and phys. Vol. XVII, p. 517 522; XVIII, p. 62 65; p. 203 207,

p. 411415.
G. Bellonci. Sur la structure et les rapports des lobes olfactifs dans les

Arthropodes superieurs et les Vertebres. Arch. ital. de biologic. T.

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Les lobes optiques des oiseaux. Note preliminaires. Arch. ital. de
biologic. T. IV, p. 21 26.



190

1884. G. Bellonci. La termination centrale du nerf optique chez les Mammi-

feres. Arch. ital. de biologic. T. VI p. 405 412. Also in: Mem.

d. r. accad. d. sci. Bologna. Ser. 4; T. VI, p. 199 204. 1885.
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d. sci. nat. Ser. 6. T. XVII. Nerv.syst. p. it; 31. (April 1883.)
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sci. nat. Ser. 6. T. XVII.
Etudes histologiques etc. Deuxieme memoire. Le ganglion optique de

la Libellule (/Eschna maculatissima) ibid. T. XVIII.
Ed. van Beneden & Ch. Julin. Le systeme nerveux central des Asci-

dies adultes et ses rapports avec celui des larves urodeles. Arch, de

biologie. T. V.
Franz Vejdovsk^". System und Morphologic der Oligochaeten. Prag.

Nervensystem p. 79 96.
Arnold Lang. Die Polycloden des Golfes von Neapel etc. Fauna und

Flora d. Golfes v. Neapel. (Zool. Stat. Neapel.) XI Monogr. Nerv.

syst. p. 164 190. Histologie. p. 182.

A. S. Packard. On the structure of the brain of the sessileeyed Cru-
stacea. National academy of sciences vol. III. Washington Apr. 1884.
Julien Fraipont. Recherches sur le systeme nerveux central et peri-

pherique des Archiannelides etc. Archives de biol. T. V. p. 243 304.
Remy Saint-Lou p. Recherches sur 1'organisation des Hirudinees. Ann.

d. sci. nat. Ser. 6. T. XVIII. Nerv.syst. p. 4763.
Alexander Foettinger. Recherches sur 1'organisation de Histriobdella

homari, P. J. van Beneden, rapportee aux Archiannelides. Arch, de

biologie. T. V. Nerv.syst. p. 445 453.
Livio Vincenzi. Note histologique sur 1'origine reelle de quelques nerfs

cerebraux. Arch. ital. de biologie. T. V. p. 109 130.
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Centralnervensystem. Arch. f. Anat. u. Entwicklungsgesch. 1884. p.

453460.
W. S. C o 1 m a n. Notes on the minute structure of the spinal cord of a

human foetus. Journ. of anat. & phys. Vol. XVIII, p. 436 441.
A. D. Onodi. Ueber die Entwickelung der Spinalganglien und der Ner-

venwurzeln. Internat. Monatschr. f. Anat. u. Hist. Bd. I, Heft. 3 & 4

(1884).

1885. G. Pruvot. Recherches anatomiques et morphologiques sur les systeme

nerveux des Annelides Polychetes. Arch. zool. exp. et gen. Paris.
Ser. 2. T. Ill p. 211336.

E. Rohde. Beitrage zur Kennt uns der Anatomic der Nematoden. Zoo-
logische Beitrage von A. Schreider. Breslau. Bd. I. Nerv.syst. p.
1218.



1885. Franz Ley dig. Zelle und Gewebe. Bonn. p. 5 7 und 164 209.

J. Poirier. Contribution a 1'histoire des Trematodes. Arch. zool. exper

et gen. Paris. Ser. 2. T. III. Nerv.syst. p. 598 613.
Hans Gierke. Die Stutzsubstanz des Centralnervensystems. Arch. f.

mikr. Anat. Bd. XXV, p. 441 554 (1885); Bd. XXVI, p. 129228

(1886).
A. D. n o d i. Ueber die Gangliengruppen der hinteren und vorderen

Nervenwurzeln. Centralblatt f. die medicinischen Wissenschaften.

1885, Nr. 1 6 und 17.
Livio Vincenzi. Sulla morfologia cellulare del midollo allungato e istmo

dell'encefalo. Memorie della r. accad. d. scienze d. Torino. Ser. 2

Tom. XXXVII.

Sull' origine re ale del nervo ipoglosso. Atti della r. Accad. delle
scienze de Torino. Vol. XX, p. 798 806.

Sull' origine reale del nervo pneumogastrico. Comunic. preventiva.
Gazz. delle cliniche. Vol. XXI, p. 209 211.

A. A. Torre. Sulla cariocinesi nel tessuto nervoso. Gazz. delle cliniche.

Vol. XXI, p. 282.
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nervoso. Milan o.
Be la Halle r. Untersuchungen tiber marine Rhipidoglossen. II Textur des

Centralnervensystemes und seiner Hiillen. Morph. Jahresbuch. Bd.

XI, p. 321436. 18851886.
Fridtjof Nansen. Bidrag til Myzostomernes Anatomi og Histologi.

Bergens Museum. Bergen 1885. Nerv-syst. p. 10 40, 71 75.
886. Franz von Wagner. Das Nervensystem von Myzostoma (F. S. Leu-

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A. D. Onodi. Ueber die Entwickelung des sympatischen Nervensystems.

Arch. f. mikr. Anat. Bd. XXVI, p. 61 80, 553 590.
Fridtjof Nansen. Forel0big Meddelelse om Undersogelser over Cen-

tralnervesystemets histologiske Bygning hos Ascidierne samt hos Myxine

glutinosa. Bergens Museum's Aarsberetning for 1885.

Preliminary Communication on some investigations upon the histolo-
gical structure of the central nervous system in the Ascidia and in
Myxine glutinosa. Ann. mag. nat. hist. London. Ser. 5. Vol. XVIII
p. 209 226.

J. Niemic. Untersuchungen iiber das Nervensystem der Cestoden. Arb.
a. d. zool. Inst. Wien u. d. zool. Stat. Triest. Tom. VII. Heft. I
p. i 60.

Gustav Fritsch. Ueber einige bemerkenswerte Elemente des Central-
nervensystems von Lophius piscatorius, L. Arch. f. mikr. Anat. Bd.
XXVII p. 1331.

F. H. Herrick. Notes on the embryology of Alpheus and other Cru-
stacea and on the development of the compound eye. John Hopkins
university circulars. Vol. VI, No. 54, p. 42 44. Baltimore.



192

1887. W. B. Ransom and D'Arcy W. Thompson. On the spinal and

visceral nerves of Cyclostomata. Zool. Anzeiger. IX Jahrg., p. 421

426. 1886.
Nicolaus Kleinenberg. Die Entstehung des Annelids aus der Larve

von Lopadorhynchus. Zeits. f. wiss. Zool. Bd. XLIV. Neuromuske-

system p. 58 151.
Emil Rohde. Histologische Untersuchungen iiber das Nervensystem der

Chaetopoden. Sitzber. d. k. pr. Akadem. der Wiss. Berlin. XXXIX

p. 781 786. Juli 1886. Translated in: Ann. mag. nat. hist. Ser. 5.

Vol. XVIII p. 311316. 1886.
Michael v. Lenhossek. Untersuchungen iiber die Spinalganglien des

Fsosches. Arch. f. mikr. Anat. Bd. XXVI, p. 370 453;
G. Fritsch. Uebersicht der Ergebnisse einer anatomischen Untersuchung

iiber den Zitterwels (Malopterus electricus). Sitzungsber, der k.

preus. Akad. der Wissensch. Berlin. XLlX. L. 2 Decemb. i886 r

p. 11371140.
F. Ley dig. Die riesigen Nervenrohren im Bauchmark der Ringelwurmer.

Zool. Anzeiger No. 234. 1886.
Romeo Fusari. Richerche intorno alia fina anatomia dell' encefalo del

Teleostei. Nota preventiva. Bollettino scientifico N. 2, Giugno 1886.

Pavia.
1887. Bela Halle r. Ueber die sogenannte Leydig'sche Punktsubstanz im Cen-

tralnervensystem. Morph. Jahresbuch. Bd. XII. 1887. p. 325 332.

During the printing of the present memoir the following papers of interest
to our subject have appeared:
1887. Bernhard Rawitz. Das centrale Nervensystem der Acephalen. Jenaische

Zeitschr. f. Naturwissenschaft. Bd. 20, p. 386461.
Julius Waldschmidt. Zur Anatomic des Nervensystems der Gymno-

phionen. Jenaische Zeitschr. f. Naturwiss. Bd. 20, p. 461 476.

1887.
L. Edinger. Vergleichend-entwicklungsgeschichtliche Studien im Bereich

der Gehirn-Anatomie. Anatom. Anzeiger. Bd. II. No. 6, p. 145

143. (Marz 1887.)
H. Viallanes. Etudes hist. etc. Quatrieme memoire. Le cerveau de la

Guepe (Vespa crabro et V. vulgaris). Ann. sci. nat. Ser. 7. T. 2.
Alfred Sanders. Contributions to the anatomy of the central nervous

system in vertebrate animals (Plagiostomata). Phil, trans. Royal.

Soc. London. Vol. 177. Part II, p. 733 766. (Read. Jan. 1886.)
A. A. W. Hubrecht. Report on the Nemertea collected by H. M. S.

Challenger during the years 1873 76. Zool. Chall. Exp. Part. LIV.

1886 vol. XIX. Nerv.syst. p. 73 90.
W. Bechterew. Le cerveau de I'homme dans ses rapports et connexions

intimes. Arch, slaves cle biologic. T. Ill, Fasc. 3, p. 293 321

(Mai); T. IV, Fasc. I, p. 130 (Juillet).



193

1887. Willy Kiikenthal. Ueber das Nervensystem der Opheliaceen. Jenaische

Zeits. f. Naturwiss. Bd. XX, p. 511 580.
Michael v. Lenhossek. Beobachtungen am Gehirn des Menschen.

Anat. Anzeiger. Bd. II. No. 14, p. 450 461. Juni.
A. Koelliker. Die Untersuchungen von Golgi iiber den feineren Bau des

zentralen Nervensystems. Anat. Anzeiger. Bd. II. No. 15, p. 480

-483 (Juli).
Charles Julin. Le systeme nerveux grand sympathique de l'Ammocoetes

(Petromyzon Planeri). Communication prelimiuaire. Anat. Anzeiger II

Jahrg. Nr. 7, p. 192 201. 1887.
Romeo Fusari. Untersuchungen tiber die feinere Anatomic des Gehirnes

der Teleostier. Intern. Monatschr. f. Anat. u. Phys. Bd. IV, p. 275

-300.1)



J ) Last winter I wrote a paper: Uber das Nervensystem der Myzostomen,
which was going to be published in Jenaische Zeitschr. f. Naturwiss. but which is
not yet appeared as far as I know. As that paper was written before the investigations,
above described, had been finished, there are some remarks on the nervous system
of various animals which do not quite agree with the results we have here obtained.



Explanation of the plates.

Plate I.

The illustrations are drawn under the camera lucida, from the
microscope directly upon the stone. The preparations (exept fig. 5 & 6)
were' fixed i chromo-aceto-osmic acid and stained with haematoxylin.
Fig. I. Homarus vulgaris. (Magnified 60 diameters ; Zeiss AA, 2.)
Transverse sections of an oesophageal commissure, a Ex-
ternal sheath, b Layer of connective tissue inside the
ext. sheath, c Inner layer or sheath of connective-tissue
closely applied to the contents of nerve-tubes (compare
fig- 5.' ) t, ^> ti Large nerve-tubes with more or less
concentrated axes, f Large nerve-tubes with no axis.
nt Central bundle of largish nerve-tubes, snt Masses of
small nerve-tubes, more peripherically situated.
2. Homarus vulgaris. (Magnified 950 diameters; Zeiss. Horn,
im. V 18 , i.) A part of fig. i, representing some smallish
nerve-tubes of various sizes, more highly magnified. The
transsected primitive tubes, of which the contents of the
nerve-tubes are composed, are distinctly visible as round
meshes. I, t Largish nerve-tubes in which a concentration to-
wards an axis is visible, t', f Small nerve-tubes ; in one of them
a slight concentration towards an axis is visible, j" Small
nerve-tube in which no concentration towards an axis is
visible, a Vacuoles. b Neuroglia-substance. c The sheath
of a large nerve-tube which is illustrated in fig. i, ^.
d Vacuoles in some nerve-tubes, probably artificially pro-
duced, k Neuroglia-nuclei.

3. Homarus vulgaris. (Magnified 950 diameters; Zeiss. Horn,
im. Vis* I -) Transverse section of a large nerve-tube
with axis (it is the same tube which is illustrated in
fig. i, t 1 ). a Neuroglia-sheath. b Sheath of another large
nerve-tube.



195

Fig. 4. Homarus vulgar is (Magnified 950 diameters; Zeiss. Horn,
im. Vis* x )- Longitudinal section of the same nerve -tube
as is illustrated in fig. 3 (of the same piece of an oeso-
phageal commissure was first taken transverse sections,
and subsequently longitudinal sections, a, a? Deeply staining
axis, b Externel layers of primitive tubes which are
samewhat obliquely transsected. c & d Neroglia-sheath of
the nerve-tube, which on one side (c) is considerably
thicker than on the other. Jc Neuroglia-nucleus situated
inside the sheath.

5. Neplirops norvegicus. (Magnified 950 diameters; Zeiss.
Horn. im. Vis* I -) Transverse section of nerve-tubes,
from an oesophageal commissure, a Inner layer of the
connective-tissue surrounding the bundle of nerve-tubes
of the commissure (compare fig. i, c). b Outer layer of
the same connective-tissue (compare fig. I, &). t, t Trans-
sected nerve-tubes; in the right one is a very slight
concentration towards a deeply staining axis visible.
t', t", t 1 " Nerve-tubes with vacuoles, which possibly, to
some extent, are transsected tubes. t { Nerve-tubes con-
taining solely large meshes, which possibly are transsected
tubes, c Vacuoles. Jc, #,, Jc', Jc", k 1 " Neurogla-nuclei and
nuclei of the connective-tissue, k' Neuroglia-nucleus situated
inside the sheath of a nerve-tube. The preparation was
fixed in Lang's fluid (corrossive sublimat 1 2 %) an d stained
with hcemotoxylin.

6. Nephrops norvegicus. (Magnified 1700 diameters; Zeiss.
Horn. im. y, 8 , 3-) ? art of the contents of a nerve-tube
highly magnified to show the walls of the primitive tubes.
a Thickenings in these walls along the concreting edges
of the tubes. From the same preparations as fig. 5.

7. Homarm vulgar is. (Magnified 190 diameters; Zeiss CC, 2).
Transverse section of a small peripheral nerve containing
large and small nerve-tubes, t Large nerve-tubes; their
sheaths are very thick and consist of several layers.
n t Small nerve-tubes, s Septa, dividing the small nerve-
tubes into bundles. Jc Neuroglia- and connective-tissue-
nuclei.

8. Homarus vulgaris. (Magnified 1150 diameters; Zeiss.
Horn. im. ! / 18 , 2.) Transsected nerve-tubes from a peri-
pheral nerve, nt Small nerve-tubes containing some few

13*



- 196 -

primitive tubes only. p,p Thickenings along the concret-
ing edges of the sheaths of the small nerve-tubes, t Large
nerve-tubes outside the scheath of which a neuroerlia-

o

nucleus is situated.

Fig. 9. Nereis virens. (Magnified 950 diameters; Zeiss 1 / 16 , i.)
Longitudinal section of a large nerve-tube (b) and some
small nerve-tubes (nt) from the ventral nerve-cord, a Sheath
of the large nerve-tube (&). The spongioplasmic walls
of the primitive tubes of the nerve-tubes are distinctly
seen longitudinal transsected.

10. Nereis vifens. (Magnified 950 diameters; Zeiss Vis l -)
Transverse sections of some large nerve-tubes running
centrally along the ventral nerve-cord (compare fig. 14).
a Central fibrous septum dividing the nerve-cord longi-
tudinally into two lateral cords (cf. fig. 14). 6 & b' Trans-
verse bundles of neuroglia-fibres ; subdividing into branches
(c, c). t, t Large central nerve-tubes. t lt t 2 t z Somewhat
smaller nerve-tubes, more ventrally situated, nt Small
nerve-tubes, nt 1 Small nerve-tubes situated between the
large central nerve-tubes (t) and the central septum (and
the transverse bundles of fibres [b]). k Neuroglia-nucleus
situated in the ventral, reticular part (B) of the central
septum (a).

ii. Lumbricus agricota. (Magnified 500 diameters; Seibert
Vs, Zeiss 2.) Transverse section of the three colossal
nerve-tubes (,, t, t) and a part of the dotted sub-
stance (c). a Connective-tissue outside the perineu-
riuin. 6 Perineurium (Vignal's gaine troisieme), outside
which the layer of muscles (m, m) is situated, d Neu-
roglia extending inside the perineurium, between the three
colossal nerve-tubes, s, s, s Septa or very thick fibres
occurring in this neuroglia and connected with the peri-
neurium. c Dotted substance, exhibiting a reticulation
produced by a transsection of tubes, nt Transsected
nerve-tubes, k Neuroglia-nuclei.

Plate II.

Fig. 12. Homarus vulgar is. (Magnified 330 diameters; Zeiss. Apochr.
4,0, 0,45, I. Cam. luc.) Large nerve-tubes from an oeso-
phageal commissure, seen in the live state in the commissure.






197 -

A&B Large nerve-tubes with striated axes (c, d). a, a Neu-
roglia layers between the nerve-tubes. I Small nerve-
tube with a visible longitudinal striation. e, e Small nerve-
tubes without visible striation.

Fig. 13. Homarus vulgaris. (Magnified 950 diameters; Zeiss. Horn,
im. Vis* J - Cam. luc.) Large nerve-tubes (a, a) from a
peripheral, abdominal nerve, and seen in the nerve in the
live state ; no striation is visible, ft Sheaths of the nerve-
tubes, c, c, c 1 Apparent septa, optic illusions produced
by a slight bending of the nerve-tubes and their sheaths.
k Neuroglia-nucleus situated inside the sheath of the
one nerve-tube.

14. Nereis virens. (Magnified 190 diameters; Zeiss. CC, 2.
Cam. luc. direct upon the stone.) Transverse section of
the ventral nerve-cord, cu External cuticulum. ep Thick
ectodermal epithelium, outside the ventral nerve-cord.
k Nuclei of the high cylindrical cells of this ectoderm.
ep { The common ectoderm of the body. k> The nuclei
of this ectoderm, n, sh Connective or neuroglia tissue
surrounding and enveloping the ventral nerve-cord, k' k"
Nuclei of this tissue. &, Similar nuclei, situated more
ventrally, towards the ectodermal epithelium, from the
nuclei of which they are not easily distinguished.
gc & gc y Ganglion cells, m, m Membrane separating the
ectoderm and the ventral nerve-cord from the inner layers
of the body. (From a preparation fixed in Flemming's
chromo-aceto-osmic acid and stained with Delafield's
haematoxylin.)

15. Homarus vulgaris. (Magnified 620 diameters; Zeiss F, i.
Cam. luc.) Isolated, largish nerve-tubes from an oeso-
phageal commissure, macerated in acetic acid (i), glyce-
rin (i) and aqua dest. (5).

16. Homarus vulgaris. (Magnified 620 diameters ; Zeiss F, I.
Cam. luc.) Isolated smallish nerve-tubes from an oeso-
phageal commissure, macerated in the same way as in
fig. 15.

17. Patella vulgata. (Magnified 620 diameters; Zeiss F, I.
Cam. luc. direct in the stone.) Nerve-tubes from a pedal
nerve-cord and a peripheral nerve, macerated as above.

1 8. Patella vulgata. (Magnified 620 diameters; Zeiss F, i.
Cam. luc.) Nerve-tubes macerated as above, stained with
picro-carmine.



198

Fig. 19. Patella vulgata. (Magnified 620 diameters; Zeiss F, I.
Cam. luc. direct upon the stone.) Transverse section of
a nerve, from which two smaller nerves (a and &) later-
ally issue, v Vental side of the nerve, a & 6 Trans-
versally transsected nerve-tubes of the small lateral nerves,
a' & b' Longitudinally transsected nerve-tubes of the same
nerves, c & d Large nerve-tubes, transversally transsected
s, s Septa dividing the nerve into bundles of nerve-tubes.
s', s' Septa separating the nerve-tubes of the two small
lateral nerves from the rest of the large nerve. / Neu-
roglia-cell with nucleus situated inside the neurilem -sheath
k Neuroglia-nuclei. (From a preparation treated with
osmic acid (i %) f r 4& hours, stained with Delafield's
haematoxylin and decoloured in water to wich some drops
of acetic acid had been added ; the section was taken directly
with a razor without imbedding.)

19 A. A part of the section, illustration in fig. 19, highly mag-
nified to show the structure of the walls between the
nerve-tubes.

> 20. Patella vulgata. (Magnified 750 diameters; Zeiss F, 2.
Cam. luc. direct upon the stone.) Longitudinal section
of a peripheral nerve near its origin in the pedal nerve-
cord, gc A ganglion cell sending a protoplasmic process (jp)
towards the neurilem-sheath (sh}\ the nervous process
which runs longitudinally was not distinctly visible in
this section. k, k', k" Circular and oblong, deeply
staining neuroglia-nuclei. n, nn, nn', nn r ' ', nn'" Ovoid, less
staining and, generally, larger neuroglia-nuclei. (The pre-
paration was fixed in chromo-aceto-osmic acid and stained
with Delafield's haematoxylin.)

21. Phallusia obliqua. (Magnified 350 diameters; Zeiss CC, 4.
Cam. luc. direct upon the stone.) Transverse section of
a peripheral nerve, sh External neurilem-sheath. (From
a preparation fixed and hardened in Miiller's fluid, stained
with acid fuchsin dissolved in turpentine with a little
abs. alcohol added.)

22. Phallusia obliqua. (Magnified 750 diameters; Zeiss F, 2.
Cam. luc. ; drawn directly upon the stone.) Longitudinal
section of a part of a peripheral nerve, a & & Septa
(longitudinally transsected) between bundles of nerve-tubes.
n Neuroglia-nucleus situated in one septum (a), ts Sheaths



199

of the nerve-tubes. The spongioplasmic walls of the pri-
mitive tubes are distinctly seen in the nerve-tubes. (From
a preparation treated as above.)

Plate IIL

The illustrations of this plate are drawn under the camera
lucida, from the microscope directly upon the stone (except fig. 23).
The preparations (exept fig. 23) are fixed in chromo-aceto-osmic acid,
stained according to Heidenhain's haematoxylin method (except fig. 24)
and some of them afterwards with Delafield's haematoxylin. All the
illustrations are taken from ganglion cells of

Homarus vulgaris.

Fig. 23. (Magnified 620 diameters; Zeiss F, i. Camera lucida.)
A & B Ganglion cells (from a ventral ganglion) isolated
in acetic acid (i), glycerin (i), and aqua dest. (5), and
stained with picro-carmine. a Space surrounding the
central bundle of primitive tubes (b) of the process, and
in which no structure is visible, n, n Neuroglia nuclei
situated outside the sheath of the cell and the process.

24. (Magnified 620 diameters; Zeiss F, i.) Part of a section
through two ganglion cells (A & B) and the neuroglia (nu)
situated between them. A & B Parts of the protoplasm
of the two ganglion cells, in which a spongioplasmic re-
ticulation is distinctly visible, cm, cm Neuroglia-sheaths
of the cells, a Transsected, spongioplasmic fibres pene-
trating, from the sheaths into the protoplasm of the
ganglion cells. & Such a fibre seen in connection with
the sheath, sp Similar fibre subdividing and forming a
reticulation, nu Neuroglia. n Neuroglia-nuclei.

25. (Magnified 350 diameters; Zeiss CC, 4.) Section through
a large ganglion cell (of an abdominal ganglion) and the
root of its process ; the lightly staining contents of which
partly originates from bundles of primitive tubes, s, s Fi-
bres penetrating from the neuoglia-sheath into the proto-
plasm of the cell, a Similar fibres transsected.

26. (Magnified 750 diameters; Zeiss F, 2.) Section through a
ganglion cell and a part of its prosess, the contents of
which arises equally from the whole protoplasm of the
cell by a convergence af primitive tubes, nu Neuroglia,
cm Sheath of a ganglion cell.



200

Fig. 27. (Magnified 620 diameters; Zeiss F, i.) Section through
a large ganglion cell and the root of its process, the
lightly staining contets (a) of which arises from a union
of bundles of primitive tubes. 6 Transsected spongio-
plasmic fibres, with which the spongioplasmic walls separat-
ing the primitive tubes, unite, cm Sheath of a ganglion cell.
28 & 29. (Magnified 620 diameter; Zeiss F. i.) Parts of suc-
cessive sections through the same ganglion cell, selected
from a series of sections to show how the lightly stain-
ing contents (p, p) of the process penetrates into the
protoplasm of the eels surrounded for some distance by
deeply staining fibres (s, s'). b Such fibres transsected.
a & s" Similar fibres penetrating into the protoplam of
the cell, cm Sheath of the cell, v, v Transsected bundles
or small masses of primitive tubes, nv Cavities in the
sheath of the cell into which cavities the protoplasm of
the cell partly extends.

Plate IV.

The illustrations are drawn under camera lucida from the mi-
croscope directly upon the stone. The preparations (exept fig. 41)
are fixed and stained in the same way as in Plate III. All the
illustrations are taken from ventral ganglia of

Homarus vulgar is.

Fig. 30 33. (Magnified 350 diameter; Zeiss CC, 4.) Successive
sections through the process of a ganglion cell, selected
from a series of transverse sections through an abdominal
ganglion. In fig. 30 the process is seen quitting the cell
in fig. 33 it is divided into two branches (a & 6). p, c Con-
tents of the process; near the cell (fig. 30) this contents
is lightly stained, in a greater distance from the cell (fig. 31)
it becomes more deeply stained until it, at a certain distance
(fig. 32), becomes quite dark, pr Protoplasm of the ganglion
cell, sf Spongioplasmic fibres, penetrating into the proto-
plasm of the cell and (sf") into the contents of the pro-
cess, s/" Similar spongioplasmic fibres occurring in the
external layers of the contents of the process, cm Neu-
roglia-sheath of the ganglion cell, is Inner neuroglia-sheath
enveloping the process, nm Concentric layers of neu-
roglia surrounding the process.



2OI

Fig. 34. (Magnified 350 diameters; Zeiss CC, 4). Transverse sec-
tion through the process of a ganglion cell, exhibiting
the concentric layers of neuroglia (nm) surrounding the
contents of the process (pc]. br Transsected side-branch,
issuing from the process the process.

35 & 36. (Magnified 620 diameters; Zeiss F, I.) Two trans-
verse sections through the same process of a ganglion
cell; selected from a series of sections, pc Contents of
the process, in which the transsected primitive tubes are
distinctly seen, sf Transsected spongioplasmic fibres
ocurring in the external layers of the contents. br, br j Trans-
sected branches issuing from the process, nm Concentric
layers of neuroglia. n Neuroglia-nucleus. b & c Similar
nuclei deeply stained.