1893-94.] Dr Gilchrist on Pallicd Gom'pUx of Dolabdla. 269 
not as in other forms, on the floor of the mantle cavity, but lies in 
the hollow formed by the junction of it with the parapodium of 
the right side, the cellular elements of the gland being indeed partly 
imbedded in the parapodial tissue, as shown in fig. 3, QJi.g. The 
unicellular elements of this gland open to the exterior, not by a 
common duct, but each glandular cell by a duct of its own. 
The position of the genital opening (fig. 3, g.of which of all the 
pallial organs shows the least tendency to shift its position, is very 
similar to that in Aplysia and Notarclius. At the genital opening 
the furrow noted before as a continuation of the mantle undergoes 
some slight modification, as shown by section E, but it nevertheless 
is distinctly continuous with and merges into the upper and larger 
lip of the genital furrow. 
General Conclusions. 
The pallial complex of Dolabella is an interesting connecting 
link and perhaps transition stage between that of Aplysia and that 
of Notarclius. The general arrangement in the parapodial cavity 
and the condition of the osphradium indicate a functional activity 
similar to that in Notarclius, and bring the animal nearer the latter 
than Aplysia. The position of the anus also is of special import- 
ance in this respect. 
But Dolabella differs both from Aplysia and Notarclius in the 
possession of the remarkable fold connecting mantle and genital 
furrow. The significance of this fold is not very apparent. It 
seems at first sight to suggest a homology between the mantle and 
the upper lip of the genital groove. We could well fancy that the 
mantle edge functioned as a sperm conductor at a time when the 
mantle cavity was further forward than it now is; that on the 
retreat of the mantle cavity, while the genital opening remained 
stationary, the mantle retained its organic connection with the 
sperm groove by means of this fold. Against this supposition, on 
the other hand, are the facts that both the genital duct and the 
hypobranchial gland are outside this fold ; that is outside the mantle 
cavity, — an unlikely condition. Perhaps the point had better be 
left for decision till something is known of the development of 
the various parts. 
Other points of importance to be considered, however, in a 
