296 SIR ©. ELIOT AND 72.22 J2 EVANS: 
connect the Tritonide with some of the olidioidea but its 
affinities are less certain. . 
~Doridoeides should probably not be regarded as a very 
primitive form. Its genital ducts are triaulic and the liver 
is elaborately ramified. Still, it obviously marks a stage 
when the characters of the Molidiide, Tritonide and Dori- 
didze could be combined in one form. ‘The doridiform shape 
is probably not important morphologically: it occurs in very 
diverse families of Gastropods (besides nudibranchs, it is 
found in the Pleurobranchide, Oncidiide, Lamellariide and 
many Chitons) where the shell is absent or small, and it is 
probably largely due to mechanical reasons. The structure — 
of the rhinophores is more significant. The jaws and radula 
are interesting for they show that these organs are practically 
the same in Bathydoris, Doridoxa, Tritonids, Dori- 
doeides and Pleuroleura, the chief difference consisting 
in the width of the radula. Narrow radulas are charac- 
teristic of the more specialized Cladohepatica, except 
Antiopella (Janus), but also occur in some species of 
Tritonia (Candiella) and Pleuroleura. As Dori- 
doeides is small, and no other form of the same structure 
is known, it may be presumed that Nature’s experiment in 
making this combination of characters has not proved a 
success. The large number of eolidiform nudibranchs 
seems to show that the cladohepatic arrangement without 
accessory branchiz answers better in active animals with 
dorsal appendages than in flat sedentary animals. The 
mantle margin of Doridoeides with the hepatic ramifica- 
tions within it corresponds to the cerata of an Atolid, but is 
less extensive in surface, less mobile and therefore less 
efficacious for aerating. 
As mentioned above, Doridoeides approaches most 
nearly to Pleuroleura of known nudibranchs, but the 
resemblances though important are somewhat general, and 
may be due to convergence. If a phylogenetic connection 
is accepted, the fact that both Pleuroleura, which is pro- 
bably fossorial, and Doridoeides, which probably lives on 
