43 
by the walls of the neural tube is irreconcilable with that at which 
I have arrived, and is I believe successfully controverted by the facts 
set forth in this paper. In a paper, soon to appear, on the develop- 
ment of Reıssner’s fibre I shall bring forward further, and possibly 
more conclusive evidence, to show that the fibre is not a secretion, 
but a nervous structure, and shall attempt to explain how it may be 
that STUDNICKA has arrived at his erroneous conclusions. 
Cambridge, Dec. 1899. 
Papers Cited. 
1) Bipper u. ©. Kuprrer, ’57. Untersuchungen über die Textur des 
Rückenmarkes und die Entwickelung seiner Formelemente. Leipzig, 
1857. 
2) ©. L. Herrıcr, ’92. Studies on the Brain of some American Fresh- 
water Fishes. Journ. Comp. Neurol., Vol. 2, p. 20—72, Pls. IV— XII. 
3) Kurscuin, ’63. Ueber den Bau des Rückenmarkes des Neunauges. 
Diss. inaug., Kasan 1863. Abstract by Srırpa in Arch. f. mikr. Anat., 
heed. 2. p. 525 530. 
4) E. Reissner, ’60. Beiträge zur Kenntniss vom Bau des Rückenmarkes 
von Petromyzon fluviatilis L. Arch. f. Anat. u. Physiol., 1860, p. 545 
—588, Taf. XIV—XV. 
5) A. Sanpers, ’78. Contributions to the Anatomy of the Central Ner- 
vous System of Teleosts. Philos. Trans. Roy. Soc. London, Vol. 169, 
p. 735— 776, Pls. LVITI—LXV. 
6) — —, ’86. Contributions to the Anatomy of the Central Nervous 
System of Plagiostomes. Philos. Trans. Roy. Soc. London, Vol. 177, 
p- 733—766, Pls. XXXVIII—XLI. 
7) — —, ’94. Researches in the Nervous System of Myxine glutinosa. 
4to London, 1894. 44 p. 8 pls. 
8) L. Srrepa, 68, Studien über das centrale Nervensystem der Knochen- 
fische. Zeitschr. f. wiss. Zool., Bd. 18, p. 1—7V, Taf. I-—II. 
9) B. Srıvuıne, ’59. Neue Untersuchungen über den Bau des Rücken- 
markes. Cassel, 1859. 
Explanation of Plates. 
Abbreviations. 
can, c. canalis centralis, cl. cerebellum. cd, d.:chorda dorsalis. coll. colliculus, 
for. M, MAUTHNER’s fibre. fbr. R. Retssner’s fibre. Job. f. frontal lobe. Job. vag, vagus 
lobe. mbr. tor, membrane covering torus longitudinalis. td. n. neural tube. det. opt. 
optic tectum. tor. lg. torus longitudinalis. v/v. cbl, valvula cerebelli. vnt. opt. optic 
ventricle. JJ, third ventricle. JV. fourth ventricle, 
Fig. 2. Pomatomus saltatrix, sagittal section of cord showing the 
canalis centralis lined by epithelial and ependymal cells, the latter sending 
long processes out through the cord; Reısswer’s fibre running the whole 
length. Coagulum about the fibre. X 100. 
