IS 
THE VOYAGE OF H.M.S. CHALLENGER. 
mantle which have overrun tlie shell. This union of the two primitive pallial nerves 
c.xplains the origin of the “ commissure ” of the stellate ganglia, so well developed in all 
the CKgojwids,' already reduced in LoVxrjo^ and still more so in the adult Sepiola 
(better marked in the embryos*), and finally disappearing in the Sepiidie and Octopods ; 
by the dis;»ppcarance of the pallial siphon and the primitive mantle, the median nerve 
luLS Wen lost, the “ commissure ” not being then any longer carried forward by this nerve 
has not j>rescrved its curvature, has become more posterior, and has passed into the 
mantle where it joins the two ganglia in a straight line.'* 
Ik-hind the stellate ganglia, the pallial nerves, preserving sensibly their diameter (PI. 
figs. 1 , 2, G, f.n ; Fig. N, iii), are directed p'osteriorly in running along the wall of 
the shell-sac, but, immediately on leaving the ganglia, they give rise to a thinner 
latero-ventml trunk (PI. V. fig. 6), innervating the mantle, and to another much larger 
one, which arrives at the fins, where it expands by dividing to an extraordinary extent, 
without, however, presenting ganglionic swellings (PI. V. fig. 6). 
Stomnto-Gmtric System. — In the Challenger specimen (the only one examined which 
was provided with a head), the “ inferior buccal ” ganglia, or stomato-gastric ganglia, have 
not been seen ; they were apparently situated under the superficial muscular layer of the 
buccal l)ulb (as they are in some degree in certain Ommatostrephidie). There can be 
no doubt of their existence ; two parallel stomato-gastric nerves run along the ventral 
face of the oesophagus and end in the large gastric ganglion (PI. VI. figs. 2, 3, gl.). 
Sense Organs. — The olfactory pits, the otocysts, and the eyes are well developed. 
The olfactoi'y pit is situated quite at the back of the ocular prominence, at 
the junction of the lateral and ventral faces of the head (PI. I. fig. 6, ol. ; PI. II. fig. 1, 
o/.). It is limited by a slightly elevated margin in the interior of which the bottom 
projects in the form of a papilla, the whole having thus the aspect of a “ circum vallate 
{Kipilhi" of the tongue of mammals (PI. VI. fig. 11).* 
Ik The otoexyst is situated between the wings of the “cranial"’ cartilage and the 
' For cxatn|iIo, in Ommat out replies (Hancock, op. cit.). 
* Von JhorinK. Vergleiclieivlc Anatoniie des Nervensysteines und Phylogenie der Mollusken, p. 257, 1877. 
’ Joutfin, Itechi-rchefl aur la coloration du tegument chez les C^phalopodes {Arch, de Zuol. Exper., s^r. 
2, t X. p. .WG, 1894). 
‘ The pallial nervea may then l)C joined to one another on the dorsal aide of the digestive tube, as they are 
likewiae in the I.amcllihmncha, )>chind nn«l at the hack of the rectum ; this enables us to understand the supra- 
recul commiwure of the Amphineura (Cliitfm, Ac.), in the identification of which were found certain difficulties 
cufiecinlly Ijing, I>-hrhuch dcr Vergleichendcn Anatomic, p. 711, 1892 ; Bouvier and Fischer, Recherches et 
oont id e ration* aur rAaym»'trio <lea Molluwjuca univalves de Cojirliyl., t. xxxii. pp. 200, 201, 1892] ; 
Grobben, Ziir Kenntnia* der Morphologic, der Verwandtschaftaverhiiltnisse und des Systems der Mollusken 
[Stlmnyilrr. Akad. W'iss. HVen, Math. Naturw. Cl., Bd. ciii. p. 85, 1894]). It is only a junction like that of 
the pallial nerve* and in no way homologoua to the visceral commissure ; the Amphineura thus re-enter into 
the rommon plan of orgnnimtion of the Molluscs. 
* The central prominence is prolmbly the i>oint of departure of the rhinophorc in form of papilla of certain 
• F^r '■)»»»• U (ChtndnUJiu, Itnralojtsis). 
