202 MR. A. HANCOCK ON THE ANATOMY OF DORIDOPSIS. 
have been observed, though there is no reason to suppose that this portion of the nervous 
apparatus is less perfect than it is in Doris. It is only under very favourable circum- 
stances that the sympathetic ganglia and the numerous delicate nervous plexuses in con. 
nexion with them can be fully traced. A great number of specimens may be examined 
before this can be done satisfactorily ; therefore my not having observed them in the 
comparatively few individuals that have been dissected of Doridopsis is not at all to be 
wondered at, especially as I have made no determined search for them. 
The cerebral ganglia exhibit in a remarkable manner the globular structure usually 
observed in the brain of the Nudibranchs. In D. gemmacea the cerebroid and branchial 
ganglia are entirely composed of numerous irregular rounded nodules, which give to 
the surface of these organs a very striking appearance. In D. nigra the cerebroid 
ganglia (fig. 6) are each broken up into four or five pretty regularly formed and sym- 
metrically arranged masses, while the branchial are more minutely divided into globules. 
The Organs of the Senses.—If the sense of smell resides in the dorsal tentacles (and 
there seems little reason to doubt the fact), it is apparently as well developed as it is in 
Doris. The tentacles have the upper portion laminated or pinnate, in the same manner 
as it is in that genus ; and the olfactory ganglia are quite as large. 
The eyes are sessile on the anterior margin of the cerebroid ganglia, close to the outer 
margin of the olfactory ganglia. They lie consequently beneath the skin, and there- 
fore cannot be very efficient organs of vision. They are, nevertheless, well developed, 
though minute. The black-pigment cup is deep and well formed, and has lying within 
it mouth a globular crystalline lens, before which is placed an arched transparent 
cornea. 
There are no organs in these animals to which the sense of taste can be assigned 
unless it be supposed to reside in the proboscis; and that it does so seems not at all 
unlikely. It ean scarcely be doubted that these animals enjoy the advantage of this 
sense; and as they possess neither tongue nor lips, nor any other surface that comes in 
contact with the food but that of the proboscis, it follows as a matter of course that this 
suctorial tube must be the seat of taste, if it exists at all in these animals; and if 
it is to be of any service to them in testing the quality of their food, it must reside 
at the anterior extremity of the organ; at least it would be most conveniently situated 
there. 
If we adopt these conclusions as probable, this proboscidiform mouth may throw some 
light on the question as to the seat of taste in the other Nudibranchiate Mollusca. Here 
we have an animal without a tongue or outer lips, and in which taste, if it exists, must 
be located in the proboscis, and most probably at its anterior extremity. Thus the 
question becomes simplified; and what we have to do is to determine, if possible, what 
part of the oral apparatus in Doris, for instance, corresponds homologically to the " 
tremity of the proboscis. First of all, if we examine carefully the anterior termination 
of this organ, there is observed a slight transverse ridge (Pl. XVII. figs. 21 & 30) 
a little way within the orifice, immediately behind the opening of the duct of the 
anterior salivary (?) glands, the margin ( f) of the orifice of the proboscis being slightly 
thickened. 
