270 



MASCULINE DEFICIENCIES IN THE BRITISH VEUTIGININ^. 

 By Hugh Watson, M.A. 



Read 11th May, 1923. 



Contents. 



PAGE 



Introduction ......... 270 



Brief descriptions of the genital organs of the specimens 



examined: ......... 270 



PAGE 



Vertigo moulinsianu (Dupuy) 270 Vertigo alpestris Alder . 273 



Vertigo antivertigo (Drap.) . 271 Vertigo pusillu Miill. . . 273 



Vertigo suhstriata (Jeffr.) . 272 Truncatellina hritannica Pils. 274 



Vertigo jpyg77(.cBa (Dxa^^.) . 272 Columella edentula (DraT^.) . 275 



The presence and absence of male organs in these specimens . 275 

 The evidence of the genital organs in connexion with the 



classification of the British Vertigininse .... 278 



Summary . . . . . . . , . 280 



Introduction. 



The researches of Dr. A. E. Boycott and others have revealed the 

 remarkable fact that snails belonging to the genera Acanthinula 

 and Vallonia very commonly have no male organs, although the 

 individuals are fully developed in other respects and have 

 spermatozoa as well as ova in the hermaphrodite gland.^ Moreover, 

 when describing the reproductive organs of Vallonia three years ago, 

 ^ I briefly mentioned that the same phenomenon occurs in at least one 

 species of Vertigo, namely, V. moulinsiana (Dupuy). Since then 

 Dr. Boycott has prepared serial sections of several other small snails, 

 chiefly belonging to the Vertigininae, and has kindly sent them to me 

 for examination. A preliminary study of these very interesting 

 slides has yielded the following results. 



Brief Descriptions of the Genital Organs of the Specimens 



Examined, 



Vertigo moulinsiana (Dupuy). 

 Two specimens collected by Dr. Boycott at Braunton, North 

 Devon, in August, 1919. — In both individuals the male organs are 

 entirely absent, except perhaps for a vestige of the first part of the 

 vas deferens adjacent to the oviduct. The hermaphrodite gland 

 consists of a single cluster of follicles containing both ova and 

 spermatozoa. The hermaphrodite duct is darkly pigmented, as is 

 often the case in the Pupillidse, and is somewhat swollen near its 



1 Boycott, Journ. of Conch., vol. xv, 1917, p. 175 ; Proc. Malac. Soc, 

 vol. xii, 1917, p. 221. Steenberg, Viden-sk. Medd. fra Dansk Naturhist. 

 Foren., vol. Ixix, 1917, p. 6. Watson, Proc. Malac. 8oc., vol. xiv, 1920, p. 17. 



