Messrs. Hancock and Embleton on the Anatomy of Kolis. 191 
separated from the main stem and become inclosed in a sheath 
of their own, and this mode of division appears to be carried on 
to a very minute degree. We have not been able to detect the 
manner in which the nerves actually terminate ; certainly we have 
seen nothing to warrant the description and the figures of M. de 
Quatrefages relative to this particular. 
On taking a review of the nervous system of Kolis, we are at 
once struck with the high grade of development, and with the 
symmetrical arrangement that obtains in it ; the heterogangliate 
character applicable to many gasteropodous mollusks being, so far 
as our researches have led us, inapplicable to this more elevated 
being. The nervous centres are closely concentrated around the 
cesophagus, and there exists a sufficient correspondence between 
them and the same organs in the Cephalopoda to enable us con- 
fidently to compare them ; indeed we have every reason to think 
that we recognise in them the homologues of the principal masses 
of the nervous centres of the Vertebrata. 
If we turn to Professor Owen’s memoir on the Pearly Nau- 
tilus, pl. 7. fig. 1, m which the nervous system is represented, 
we find that the supra-cesophageal mass or brain together with 
the attached optic lobes, taken in conjunction with the anterior 
cesophageal ring formed by the union of two ganglia, corre- 
sponds to the anterior supra-cesophageal ganglia of Kolis with 
the slender or middle collar round the cesophagus, since they 
give off nerves which go to supply analogous parts, viz. the eyes, 
tentacles, lips, &c. The posterior cesophageal ring of the Nau- 
tilus to a great extent represents in the same way the lateral 
supra-cesophageal ganglia of Holis, united with all the infra- 
cesophageal ganglia and the two large collars or commissures 
together. 
At fig. 3, same plate, Professor Owen gives a view of the ner- 
vous system of the Sepia officinalis ; the homology is equally di- 
stinct as in the former case, only the parts are more concentrated ; 
still they serve to lead us on more easily to compare the ganglia 
of Kolis with the several divisions of the more highly-developed 
nervous centres of the Vertebrata. In Holis we see that certain 
nerves of relation—of special and common sensation, and their 
corresponding nerves of motion, voluntary or reflex—are in con- 
nexion only with the two pairs of supra-cesophageal ganglia. 
The olfactory and optic nerves, and numerous others to the lips, 
mouth, tentacles and side of head and back, are thus attached ; 
hence we infer that the anterior part of the supra-cesophageal 
ganglia may be in some measure compared, though not perhaps 
quite accurately, to the cerebrum and optic lobes of the Verte- 
brata ; at all events these are the only parts to which they corre- 
spond. The posterior parts of the median cerebral ganglia, and 
