192 Messrs. Hancock and Embleton on the Anatomy of Kolis. 
the remaining ganglia together with their commissures and col- 
lars, are the representatives of the medulla oblongata and ae 
cord of the higher animals. 
We do not discern in Holis anything at all analogous to the 
sympathetic system of the higher animals. 
In the nervous system again we are sorry to be onnpetion to 
be at issue with M. de Quatrefages, who states in his paper that 
“toutes les grandes masses nerveuses sont réunies au-dessus de 
Vcesophage et d’elles seules émanent directement les nerfs qui se 
rendent dans toutes les parties du corps.” Subsequently how- 
ever he points out the presence of a single small ganglion below 
the oesophagus, from which small nervous twigs are given off to 
the mouth and digestive tube. The incorrectness of these and 
other observations we hope to have rectified. Further, M. de- 
Quatrefages makes out only one nervous cesophageal ring; we 
have over and over again seen and verified the three represented 
in our plate. The nerves of vegetative life he derives from the 
same ganglia that give off the nerves of relation, and points this 
out as an interesting fact. The rule with two or three excep- 
tions appears to be, that the two sets of nerves have two appro- 
priately distinct sets of ganglionic centres, viz. the infra-cesopha- 
geal for vegetative life, and the supra-cesophageal for the life of 
relation, which is agr eeable to analogy. With regard to the num- 
ber and arrangement of the nerves, we find M. de Quatrefages to 
be again in confusion. His number is very far short of the full 
complement, and he has traced scarcely any to their proper de- 
stination. We observe that he gives to the optic nerves a gan- 
glionic swelling which we have never seen, and omits the olfae- 
tory ganglion, which may be seen even during life im the more 
transparent species. 
We do not understand M. de Nordmann’s account of the ner-— 
vous system. It is possible that in that section of the genus 
Eolis to which Tergipes belongs, the nervous system may differ 
from that of the other divisions, but we should be surprised to 
find it so different from that of those we have dissected, as it is 
represented in M. de Nordmann’s paper. | 
The Senses. 
The organs of the senses appear to be as highly developed in 
Eolis as in any other of the Gasteropods. The sense of touch is 
spread over the whole surface of the body, including the foot, ' 
the tentacles, and the branchial papille, which last are so ex- 
tremely sensitive as to respond to the slightest undulations of the 
water around them. Many of the species indeed are so alive to 
such impressions, that it becomes a matter of difficulty to observe 
their habits, and even their natural form, since on the slightest 
