MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 
241 
higher animals. Fifthly, the visceral ganglion attached to the right branchial is the 
only evidence we have of the heterogangliate type in the oeosophageal nervous 
centres of Doris. Its nerves go to the stomach, to the respiratory organs, to the circu- 
latory and reproductive apparatus, being at these several viscera connected with their 
sympathetic ganglia. This single ganglion we take to be the representative in Doris 
of that part of the spinal cord in the Vertebrata which gives off a series of nervous 
branches, and communicates with either the chain of ganglia of the trunk of the 
great sympathetic or the plexuses more immediately attached to the several viscera. 
Sixthly, next in order come the pedial pair of ganglia, placed on a plane rather below 
the other two pairs and on the side of the sensorial. They subserve the locomotive 
organ, and hence represent those parts of the spinal cord of the higher animals, 
which also in them supply the organs of locomotion. Seventhly, the first infra-oeso- 
phageal or buccal ganglia supplying the buccal or lingual apparatus with sensation 
and motor power, and, as we suppose, with taste as well, answer to that part of the 
medulla oblongata from which the lingual and gustatory nerves arise. Eighthly, the 
second infra-oesophageal or gastro-oesophageal correspond to the gastric division of 
the pneumogastric ganglion of the medulla oblongata of vertebrate animals. 
In Doris, then, we see the pneumogastric apparatus resolved into two parts ; the 
pneumonic appears in the branchial ganglia, the cardiac is wanting, the gastric is 
seen in the gastro-oesophageal. These give off nerves, passing to the oesophagus and 
stomach, which are the counterparts of the pharyngeal branches of the glossopharyn- 
geal, and of the pharyngeal, oesophageal and gastric portions of the par vagurn of 
Vertebrata. 
The sum of these comparisons is, that the whole of the ganglia arranged in Doris 
around the top of the oesophagus are analogous to the encephalon and a portion of 
the enrachidion of the Vertebrata. 
There seems great probability that the cerebral hemispheres and the cerebellum, 
with the seats of consciousness and volition, and also of emotion of the higher animals, 
are but very faintly shadowed forth in the cerebroid ganglia of the Mollusca. 
Organs of the Senses. The organs of Hearing. — These are two very delicate, micro- 
scopic, ovoid capsules, sessile on the outer margin of the cerebroid ganglia imme- 
diately behind the eyes. When magnified considerably they show an inner and an 
outer capsule, enclosing fluid in which exists an agglomeration of minute otolithes. 
When these are more highly magnified their form is seen to be pretty accurately oval, 
presenting a central darkish spot or nucleus. When extracted with their capsule they 
present a continual vibratile motion. 
In Doris aspera the number of otolithes was found to be upwards of forty. On 
account of the very rudimentary state of the organs and their depth from the surface, 
it is evident that their function must be excessively limited. 
The organs of Sight . — These are placed immediately beneath the skin, behind the 
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