314 ON THE GENUS CUMANOTUS. 



that the hooked pads are associated with the S rather than with the 

 $ organ ... at the same time, what was observed in the Laboratory- 

 points strongly to the conclusion that they are really ? clasping organs. 

 If the organs of the one individual are called A ( c? ), B ( ? ), and 

 of the other, X ( c? ), Y ( ? ), what was observed was as follows : The 

 two individuals were placed right to right with the complete apparatus 

 of both extended and approximating. The base of A ( (? ) was grasped 

 laterally by an upward extension (i.e. presumably the pads) on both 

 sides of Y ( ? ), and the base of X ( (? ) was similarly grasped by 

 upward lateral extensions of B ( ? ). In each case a sort of peristaltic 

 movement on the part of B ( ? ) and Y ( $ ) occurred. As the grasp of 

 B ( ? ) and Y ( $ ) extensions relaxed, the flow of spermatozoa from 

 X ( (? ) and A (S) respectively was distinctly visible, while as the 

 grasp of the extensions closed round the base of X ( <? ) and A (S), the 

 flow of spermatozoa was checked." As far as I am aware, a female 

 clasping organ of this kind has not yet been recorded among Nudi- 

 branchs, but it is possible that in some other genera of aeolids its 

 nature may have been misunderstood. 



It is doubtful whether Cumayiotus' heaumonti and Cumanotus laticeps 

 are specifically the same. The identity is not improbable, but 

 Odhner's specimens (judging from the figures) had lost all the cerata. 

 Cumanotus hcaumonti is remarkable for having a short truncated body 

 and extremely long snaky cerata, but when these have fallen off the 

 Plymouth specimens look very like Odhner's figures, and have the 

 margin of the foot similarly expanded. There may also be differences 

 in the denticulation of the jaws and lateral teeth. But these are 

 slight divergences, and hardly of specific value unless associated with 

 others. Still, until a complete specimen of the Norwegian form has 

 been examined it is safer not to unite the two species, and provision- 

 ally I think the genus may be tabulated as follows : — 



Cumanotus, Odhner, 1907. 



1. C. hcaumonti (Eliot), 1906. 



2. C. laticeps, Odhner, 1907. 



If the species are united the name heaumonti has priority. 



I hope to publish figures of the living C. hcaumonti in a supplement 

 to Alder and Hancock's British Nudihranchiate Mollusca, which will 

 soon be issued by the Bay Society. 



C. laticeps is known by four specimens obtained at Sorvser, in the 

 extreme north of Norway, in 5-10 fathoms of water. C. heaumonti 

 has been captured at Plymouth, twice in Barn Pool and on several 

 occasions in Jennycliffe Bay, at a depth of 2-5 fathoms, and though 

 far from common, appears to be a resident and not merely a visitor. 



