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small, subglobular in form, and closely connected with a short 

 twisted tube*, much dilated at the middle part, and coated over with 

 a layer of dark pigment cells. It is with this tube, as above noticed, 

 the small oviduct communicates, in order, as it would seem, to permit 

 of self-impregnation, or to answer some other purpose, with the na- 

 ture of which we are unacquainted ; but there is also an intromit- 

 tent organ, which, however, I have never seen properly exserted. 



As to the affinities of Phyllirrhoe with Gasteropods, it may be ob- 

 served that the animal is bisexual, that the eyes, like those of Glaucus 

 and lanthina, are very small and rudimentary, being closely applied to 

 the ganglia of the brain, after the manner of the acoustic sacs, and 

 that both Phyllirrhoe and Glaucus agree in possessing two lateral 

 horny jaws, articulated with each other superiorly, and bordered 

 with minute conical teeth. 



In the Glaucidte, the branchiae, which consist of simple papillary 

 projections of the skin, are distributed in an equable manner over 

 the dorsal region of the body ; and any deviation from this arrange- 

 ment would naturally tend, either to a more definite localization, or 

 still further dispersion. It is the latter modification which appears 

 to have taken place in Phyllirrhoe ; so that its respiratory vessels 

 ramify minutely through the common integument, just as the vas- 

 cular trunks analogous to those which break up in the pectinate gill, 

 adapted for aquatic breathing, are subdivided, and spread themselves 

 over the smooth walls of the lung-chamber in Pulmonifera. 



As respects its affinity to the Pteropods, here too the lateral jaws 

 of Phyllirrhoe must be borne in mind, together with the almost com- 

 plete suppression of the organs of vision. It is worthy of note also, 

 that its acoustic capsules contain otokonia, as in Pteropoda, instead 

 of single globular otolithes like those of Glaucus, and there is some 

 reason to believe that the long tentacula, so called, are the homo- 

 logues of the cephalic fins of Pteropods. 



The particular features of Phyllirrhoe, expressed in the last para- 

 graph, also serve to distinguish it from the Heteropoda, but it some- 

 what approximates this order in the general conformation of its body, 

 which is elongated, laterally compressed, and presents a kind of pro- 

 boscis at the anterior, and a rudder-fin at the posterior extremity. 

 There is also, as it would appear to be, a small remnant of the foot 



* I have distinctly traced the homologue of this tube in Pteropoda, Heteropoda, 

 and the Gasteropoda proper. 



VOL. VII. 2 N 



