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NOTE ON THE GENITALIA OF THEBA CANTIANA Mont. 



By a. E. boycott. 



(Read before the Society, Dec. 8lh, 1915). 



So little is known of the physiology of the genital apparatus in 

 mollusca that it seems worth while to record observations even as 

 trivial as the following. As is well known (see e.g. C. Ashford, this 

 Journal., vol. iv., p. 269 and plate x) T. cantiana has a long (about 

 17 mm.) thin tubular organ opening into the atrium: its homology 

 is doubtful, it does not seem even to have a definite name and its 

 function is, I believe, quite unknown. In June last, near St. Albans, 



I found a pair in copula : subsequent dissection showed that the act 

 was so far complete that spermatophores had been exchanged and 

 were found in the ducts and vesicles of the spermathecse. The 

 " doubtful organs " appeared abnormally short and bulky : they are 

 shown at C and D in the figure compared with those (A and B) 

 from two individuals exhibiting no signs of sexual activity, taken at 



