OF NORTH AMERICA. 11 



MALE ORGANS. The penis-sac (13) is very large, cylindrical, rather 

 wide at the external opening and gradually contracting at the distal 

 end where the penis is attached ; it is grooved along its upper surface 

 where a part of the prostate gland and the receptaculum seminis fit 

 against it in their natural position. The penis (17) is variable in 

 length but is always a tube-like body about the diameter of the vas 

 deferens and terminating in a more or less rounded head. The penis 

 and the upper portion of the penis-sac are bent back upon the latter 

 at right angles. The vas deferens (14) is a narrow white tube of vary- 

 ing length ; in its natural position it lies in two loops which run longi- 

 tudinally with the penis-sac; at the right side of the penial aperture 

 it enters the muscular tissue of the body wall where it runs in an irregu- 

 lar course and emerges near the vaginal aperture as the duct of the 

 prostate (31) ; this duct makes a long loop between the penis-sac and 

 the proximal portion of the oviduct ; as it nears the prostate it enlarges 

 somewhat and enters that organ in a central depression. The prostate 

 (30) is usually a somewhat sac-like organ, flatly cylindrical and lies in 

 a groove on the posterior portion of the penis-sac. The oviduct and 

 the duct of the spermatheca pass over its inferior surface in a groove ; 

 the first accessory albuminiparous gland lies below it and the recep- 

 taculum seminis lies posteriorly to and covers a portion of it. The outer 

 surface is very rugose and the interior is divided into many small 

 tubes. The posterior portion of the prostate (29) narrows to form 

 a ribbon-like organ, often called the male portion of the hermaphro- 

 dite duct. This portion connects posteriorly with the oviduct, with 

 which it unites to form the ovisperm duct. 



The penis-sac is protracted by two sets of muscles, one of which 

 (anterior, 15) is attached to the dorsal wall of the fore part of the 

 body, while the other (posterior, 16) is attached to the eolumella 

 muscle. There is a penis-sac retractor (19) and a penis retractor (18) 

 which have their insertions in the eolumella muscle. The male sys- 

 tem is innervated by a nerve from the cerebral ganglion which con- 

 sists of two branches, one extending to the head of the penis while the 

 other innervates the penis-sac. The penis-sac is a large tube with 

 muscular walls, somewhat corrugated within, where there are also one 

 or two distinct folds (plate IV, fig. H). 



FEMALE ORGANS. The oviduct begins at the ovisperm duct where 

 it becomes much convoluted to form the so-called uterus (27). The 

 point of its commencement is underneath the anterior end of the 

 albuminiparous gland. Near the second albuminiparous gland it be- 

 comes smooth and rounded (26), is later embraced by the large first 



