MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 
243 
In Doris we have a similar form, that of laminse, attached to a central stem, which is 
ordinarily erect and exposed, but is capable in most species of being" retracted within 
a cavity. These tentacles are placed on each side of the median line, at the anterior 
extremity of the body, over the head. 
The subject of the nature and signification of the dorsal tentacles has been more 
fully discussed in our paper on Eolis, before alluded to ; it is therefore perhaps unne- 
cessary for us here to dwell more at length upon it. 
The organ of Taste. — Is doubtful as to its existence ; its use may be in some mea- 
sure subserved by touch, it probably resides in the different lips and the passage to 
the buccal cavity, or may have its special seat in that cavity itself. The tongue, 
which is peculiarly a prehensile organ, seems very ill adapted for an organ of taste. 
The organ of Touch. — This is the skin, over which the senseis universally diffused ; 
but the faculty is undoubtedly specialized also in the oral appendages, whether these 
have the ordinary linear form of tentacles, or exist as a veil-like expansion partially 
encircling the mouth. 7''he veil and the tentacles are alike the homologues of the 
oral tentacles of Eolis, and are supplied like them with nerves coming off from the 
anterior part of the cerebroid ganglia. The tentacles or veil are so placed that they 
can with perfect ease be applied to the surface of substances on which the animal 
crawls or seeks its food, and to the food itself ; and there is every reason to believe 
that the sense of touch residing in these organs is exquisitely delicate. 
We have not yet been able to examine with sufficient care the minute structure of 
the skin ; at present we can only offer the following particulars. The skin in most 
species is tough and coriaceous, and is of a spongy or cellular structure wdthin : the 
cloak, in all the British species examined, is stiffened with numerous imbedded 
spicula, having a more or less symmetrical arrangement. Spicula are also observed in 
the foot, in the tentacles, and in the roots of the branchial plumes. The under sur- 
face of the foot and the upper surface of the cloak, as before stated, are covered with 
vibratile cilia. The branchial plumes and dorsal tentacles are also furnished with 
them. 
Explanation of the Plates. 
PLATE XI. 
Fig. ] . General view of viscera of Doris pilosa seen from above, the dorsal skin and 
peritoneal membrane having been laid open, a, buccal mass ; b, upper 
surface of stomach ; c, pancreas; d, intestine; e,e, liver; f mucus-gland 
belonging to female organs ; g, portion of testis ; h, spermatheca; i, acces- 
sory spermatheca ; j, pericardium, exhibiting through its transparent wails 
the ventricle and auricle; k, ventricle; I, auricle; m,m, two lateral venous 
