54 PROCEEDINGS OF THE M.VLACOLOGTCAL SOCIETY. 



it was frequently found that this muscle arose from two quite 

 independent points. In all the specimens of A. liisitanicus, Mab.,^ 

 which I have examined I have found the position ([uite constant. 



In Limax, Testacella,^ and Helix similar variations were not 

 uncommon. 



In LimncBa stagnalis, L., the variations, while not important, were 

 very numerous. Baudelot,^ in his beautiful drawings of the generative 

 anatomy of this species, figures three groups of retractor muscles 

 which spread themselves out along the penis and its appendix, and 

 may be readily divided into seven distinct muscles. Specimens very 

 similar to this have been seen by the writer, and also others in which 

 there were but two distinct muscles, these being attached to the lower 

 portion of the appendix. 



From an examination of a fairly representative series of each of 

 the species previously mentioned I may briefly summarise my results 

 as follows : — 



1. No variation whatever was found in the form, number, 



or position of the buccal retractor muscles. 



2. The tentacular retractor muscles are quite as constant, very 



slight variations only being found in the labial branches. 



3. While the genital retractor muscles may be constant in some 



genera, in Avion, Testacella, Limax, Helix, and Limncea 

 innumerable variations were found. 



4. No great specific value can be attached to the myology in the 



above-mentioned genera, and its generic value is probably 

 much less than that of the nervous, generative or digestive 

 systems in the Pulmonate Mollusca generally. 



1 The Conchologist, 1892, vol. ii. p. 59. 



2 Aunals and Mag. N.H. 1893 (ser. vi.), vol. xii. p. 24. 



^ Recherches sur I'appar. Gen. d. Moll. Gasterop. 1863, pi. iv. fig. 1. 



