OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 469 
OxssERvations om the CrantaL Nerves of Scyturum. By A. 
Mitnes Marsnatt, M.A., D.Sc., Professor of Zoology in 
Owens College; and W. Batpwin Spencer, of Owens 
College. (With Plate XXVIT.) 
Part I. The Preauditory Nerves. 
Tue investigations recorded here were undertaken in the first 
instance for the purpose of controlling certain. determinations 
published by one of us in a previous number of this journai! 
concerning the cranial nerves of Hlasmobranchs. To this end 
we have carefully re-examined the specimens upon the investiga- 
tion of which the former account was based, and have, in addi- 
tion, made a large number of new preparations, illustrating more 
especially the later stages of development—stages m to Q of 
Balfour’s nomenclature.” 
During the course of our work so many altogether new and 
unexpected points were brought to light, that we soon found it 
necessary to widen considerably the scope and limits of our in- 
vestigations, and have finally been led to attempt a complete 
account of the development of the cranial nerves from stage K to 
the adult form, and to endeavour in this way to connect together 
directly the accounts previously given of the early stages® with 
the descriptions of the nerves of adult Elasmobranchs published 
by Stannius,* Gegenbaur,’ and other anatomists.® 
Owing to defective supply of materials, our observations on 
the stages earlier than kK are too fragmentary to be reliable; this 
we greatly regret, inasmuch as many features in the early stages 
are of extreme importance, and would well repay thorough in- 
vestigation. | 
In the present paper we propose to confine ourselves to the 
consideration of the preauditory nerves, reserving the postaudi- 
tory, which preseut many features of peculiar interest, for a 
future occasion. 
' Marshall, “On the Head Cavities and Associated Nerves of Elasmo- 
branchs,” ‘Quart. Journ. Micr. Sci.,’ Jan., 1881, pp. 71 seg. Future 
references will be to this paper unless otherwise specified. 
5 Elasmobranch fishes, pp. 79 and 80. 
3 Balfour, op. cit. Marshall, loc. cit. 
* Stannius, ‘Das peripherische Nervensystem der Fische,’ Rostock, 
1849, 
° Gegenbaur, “Die Kopfnerven von Hexanchus,” ‘Jenaische Zeit- 
sehrift,’ Bd. vi. 
6 Hsp. Jackson and Clarke, “The Cranial Nerves of Zehinorhinus 
spinosus,” * Journal of Anatomy,” vol. x. 
