Cerebral Tract of Professor Owen. 283 
sepie is situated. This view answers well enough in making 
the two portions of*the beak of Sepia to correspond with the 
avian beak; and no doubt the spiniferous lamina may equally 
well be considered as either the tongue or the palate. But it 
may be objected that, according to this view, the umbilical 
canal would enter the body on the neural or dorsal aspect, the 
aural sacs would be wrongly placed, also that the ventral or 
hemal surface is more highly coloured, and that the young 
sepia, when progressing, prefers that surface to be upwards, 
like the vast majority of invertebrates: here also is lodged 
the os sepia, the analogue, though by no means the homolo- 
gue, of aspine. ‘The great nervous tracts of the mantle too, 
though they arise from the subcesophageal ganglia, are directed 
towards this aspect; and if any tracts must be considered as 
spinal, these, through all the Mollusca, seem to correspond, 
though'the primitive annular disposition of a ring or loop 
remains. 
The situation of the ganglia in the invertebrate is deter- 
mined by that of the locomotive, prehensile, and respiratory 
organs, the only type of formation recognizable. Thus the 
helix, with its feot homologous to that of the sepia, though 
entirely postoral and undivided, has its lower parts much as 
in Sepia; in Aplysia, having lateral processes of the body, 
the ganglia in question are lateral; and in Doris, with its 
strong mantle above and weak foot below, all the ganglia of 
the rmg form one mass on its upper part, it being only com- 
pleted by a commissure. Other objections to the theory that 
by reversing surfaces and change of nomenclature the sepia 
becomes tantamount to a bird, are that the relative position 
of the liver and alimentary canal do not seem to correspond, 
and the situation of the main artery would also be ventral, 
whilst the vein would be on the opposite aspect. Cer- 
tainly the heart and the respiratory organs, which. in the 
sepia may, according to the old nomenclature, be said to be 
ventral, are in many lower mollusks dorsal; but this has no 
relation to the question, but is due rather to what Cuvier 
terms the conditions of existence *. 
Admitting the originality and truth of the Professor’s main 
view, is it certain that the transfer of the oral opening has 
* We have elsewhere (Ann. & Mag. Nat. Hist., May 1877) endea- 
voured to explain the different situations of the shell and its relative 
development in the sepia, nautilus, argonaut, and in Gastropods. In the 
first the cellular part (valgo bone) is only partially present and is dorsal; 
in the second and third the expanded part is present on the ventral side ; 
whilst in the snail or whelk its expansion (as well as the branchiee) is 
dorsal; but this is from the torsion of this part of the body, and the 
ascension, as it were, of the branchie and the nerves, &c. 
igke 
