i6 



!■ KM) 1 IllOf- HKI.AM). 



iM.-X. Kl. 



to its ii|)pcr jjaii, close under the bladder, and a stronger braneli lor the 

 oviducl. riic latter branch insérâtes relatively high on the latter, but 

 proceeds downwards, ])artiall_y ensheathing the oviduct. In rare cases the 

 two branches of the retractor are separated frrjin their origin, or with onl}- 

 faint indications of a connection. 



P)oth the oviduct, the cijiphallus and t.h<: stalk' of the receptaculum 

 open into i\\v dlriiiiii \(itr.\, thai part ot ih(; reproductive organs which presents 



ree. 



Fig. lo. Lower parts of the reproductive organs oi Arioii atcr, 6/1. 



atr. atrium genitale, cp. epiphallus, o. oviduct, o.-sp.-d. ovispermatoduct, rec. receptaculum, 

 •v reir. retractor, v. d. vas deferens. 



certain noticeable features. It varies in shape, in larger specimens often 

 being constricted into an upper and a lower part separated by a furrow 

 (as a rule in var. atra), which, however, can be absent to a greater or lesser 

 degree (compare fig. lo to fig. 12). In young specimens the lower part 

 of the atrium is only represented by a slender ribbon, and the upper part 

 generally has a very distinct prominence, ?i. lateral recess (fig. 11, /. r.). In 

 older specimens, too, this may be very powerfully developed, but as a 

 rule this is not the case in the common var. atra (compare fig. 10 to fig. 12). 

 In the cavity of the upper part of the atrium we find the voluminous ligttla, 

 attached close to the opening of the oviduct, and, folded up in the shape of a 

 cone, with its top pointing to the genital aperture. When unfolded, the surface 



