of Ommastrephes todarus. 13 



leads to the same conclusion. We shall not, however, on this 

 occasion endeavour to trace out the homologies which we believe 

 to exist between the organs of the Cephalopods on the one hand, 

 and the organs of the rest of the Mollusca on the other. To this 

 important and highly interesting subject we hope to return, when 

 a more extended knowledge of the anatomy and physiology of 

 these highly organized animals shall have enabled us to speak 

 with sufficient confidence. 



EXPLANATION OF PLATES L IL 

 Plate I. 



Fig. \. Ventral view of the cephalic ganglions and nerves of O. todarus : — 

 a, anterior suboesophageal mass ; h, median ditto ; c, their imder 

 commissure ; d, upper ditto ; e, visceral ganglion ; /, /, branchial 

 ditto ; g, g, stellate ditto ; h, cords or commissures uniting same 

 to branchial ganglions ; % transverse commissure of stellate gan- 

 glions ; j, upper buccal ganglions ; k> lower ditto ; I, commissure 

 uniting the two pairs of buccal ganglions ; m, commissure uniting 

 upper buccal ganglions to anterior suboesophageal mass ; n, com- 

 missure between the same buccal ganglions and optic ganglions ; 

 0, o, brachial nerves ; jo, nerves to muscles of outer buccal capsule ; 

 q, q', nerves to muscles of buccal mass and jaws ; r, lingual nerves ; 

 s, oesophageal nerves or par vagum ; t, t, two pairs of small nerves 

 lost in muscles in front of the eyes ; u, u', u", nerves to the mantle 

 and its muscles ; v, v, two pairs of nei-ves to skin of head above 

 and behind ; w,w', nerves applied to the anterior aorta ; x, x, great 

 posterior sleeve nerves ; x', x\ nerves to fin -, y, y, sleeve nerves ; 

 z, visceral nerves. 



Fig. 2. Enlarged view of anterior and median suboesophageal, visceral, 

 and branchial ganglions : — «, anterior mass ; b, median ditto ; 

 c, under commissure of same ; d, d, upper ditto ; e, visceral gan- 

 glion ; /,/, branchial ditto ; h, h, commissure uniting branchial 

 and stellate ganglions ; i, nerves supplying funnel ; j, auditory 

 nerves ; k, k, optic ditto ; o, o, o', o', brachial ditto ; p,p, ganglionic 

 swellings of same; q', q', nerves to oral lamina, exhibiting gan- 

 glionic swellings q, q ; t, t, two pairs of nerves to muscles in front 

 of eyes ; u, u, nerves to mantle ; z, ditto visceral. 



Fig. 3. Side view of anterior and median suboesophageal, optic, branchial 

 and visceral ganglions : — a, anterior mass ; b, median ditto ; c, un- 

 der commissure of same ; d, upper ditto ; e, visceral ganglion ; 

 /, branchial ditto ; g, g, oesophagus ; h, h, commissures uniting 

 stellate and branchial ganglions ; i, nerves to the funnel ; j, audi- 

 tory nerves ; k, optic ditto ; Z, optic ganglions ; m, commissure 

 between upper buccal ganglions and anterior suboesophageal; 

 n, ditto uniting optic and upper buccal ganglions ; o, o, o', o', 

 brachial nerves ; p, p, ganglionic swellings of same ; v, two pairs 

 of small nerves to skin of head above and behind. 



Plate IL 



FHg. 1. View of splanchnic nervous system seen from above : — a, anterior 

 suboesophageal mass ; b, under commissure uniting same to me- 

 dian suboesophageal ; c, c, upper commissure of same ; d, upper 

 buccal ganglions ; e, under ditto ; /, commissure uniting the two 



