COLLIKGE : OBSERVATIONS ON SPECIES OF ARION. g 



obtains in A. htsitanicus, only the head is not so globose. The 

 retractor muscle is attached to the duct just where it commences 

 to expand to form the head. That attached to the free-oviduct 

 is some little distance above this point, so that the muscles run 

 in opposite directions, as shown in the figure (PI. II., Fig. 3, v.m.). 



Notwithstanding the minute differences in the form of the 

 reproductive organs, pointed out by Pollonera,t I am inclined to 

 agree, with Simroth, that the A. sidcatus, IMorelet, is identical 

 w'lih. A. empiricovmn. The A. hihernus, IMabiile, is also nothing 

 more than a variety of A . empiricovnm, differing from the typical 

 form in its smaller size, more feeble rugae, and by the lighter 

 colour of the foot-sole. 



4. Arion lusitanicus, Mabille, 1868. (PI. II., Fig. 4.) 



Not a few malacologists have mistaken this species for 

 A. riifiis, ater, or empivicoviun. Externall)' it is not unlike the 

 last-mentioned species. SimrothJ, who has described and 

 figured a series of young forms, mentions that the foot-sole is 

 without the yellow slime and has an orange-coloured edge. 

 Some young forms look not unlike A. snbfuscus, Drap. The 

 A . dasilvae, Pollonera, is regarded by Simroth as a variety of 

 this species ; at present, however, I prefer to keep it distinct. 

 The A. nohrei, Poll., is, in my opinion, synonymous wdth A. lusi- 

 tanicus. The onl}^ points of difference I find in the generative 

 organs are that there is no sharp distinction between the sperm- 

 duct and vas deferens, which are slightly shorter than in A. 

 lusitanicus, the free-oviduct is more tapering and does not show 

 the sharp bend so characteristic of A. lusitanicus. The retractor 

 muscle of the receptaculum seminis is also shorter (PI. II., 

 Fig. 5). In ^4. lusitanicus the generative orifice leads into a large 

 vestibule. The sperm-duct is long and tapering and sharply 

 differentiated from the long vas deferens. The receptacular 

 duct commences as a dilated tube, then narrows and expands 

 terminally to form the receptaculum seminis, not unlike the 

 condition which obtains in A. atev.l To the receptacular duct a 

 retractor muscle is attached, which blends with that attached to 

 the lower portion of the free-oviduct. The free-oviduct is a 

 short tube slightly bent upon itself, the lower portion being 



t Bull. Mus. Zool. Torino, 1890, vol. v., no. 87. 



t Nova. Acta. K.L.-C Deutsch. Akad. Nat., Bd. Ivi., Taf. 4. 



§ Not .-1. ewpiricoiuni, Per., as I, by an oversight, stated in a previous paper (Oonchologist, 



1893, vol. ii., pp. 113-17). 



