257] NORTH AMERICAN MONOSTOMES 39 



which opens to the exterior by a small dorsal pore. The genital glands are 

 situated in the posterior fifth of the body where they are closely packed in 

 the posterior arch of the intestine, the posterior testis almost entirely 

 filling this space. It is slightly flattened antero-posteriorly and measures 

 in its greatest dimension 1052 /i and in an axis at right angles to this, 894 /x. 

 The anterior testis situated a short distance cephalad to the posterior, 

 is spherical in shape and a little smaller, having a diameter of 894ju. The 

 two testes are separated by a particularly long loop of the uterus which 

 extends to the intestinal arch, and in some instances even beyond, and 

 usually folds back part way forming a double loop. The vasa efferentia 

 given off from the anterior margins of the two testes unite cephalad and 

 mesad to the anterior testis to form the vas deferens which takes a fairly 

 straight course to the cirrus pouch with which it unites. 



The cirrus pouch is a rather large oblong sac extending from the 

 pharynx to a short distance beyond the anterior wall of the intestinal 

 bifurcation. It opens into a small genital atrium which in turn opens to 

 the exterior, ventral to the pharynx. 



The ovarian complex is situated opposite to and on a level with the 

 anterior testis. The ovary is very much smaller than the testes, measuring 

 434/1 in diameter. Dorsal to this is the receptaculum seminis, the duct 

 from which joins the oviduct before it enters the shell gland. The shell 

 gland, a compact spherical organ, is situated dorsal and posterior to the 

 ovary. It has a diameter of 388 ju. The vitellaria lie between the lateral 

 body wall and the external wall of the digestive crura over which they 

 seldom pass. They extend from the posterior pharyngeal region to the 

 extreme posterior end where they are separated by the excretory bladder. 

 The vitelline glands are made up of small follicular grape-like clusters 

 arranged along a main stem, which in the region of the anterior testis 

 gives rise to the vitelline ducts. These pass mesad and unite a short 

 distance posterior to the shell gland to form the common duct which 

 passes straight to the shell gland. It enters this at the posterior side 

 and passes through the outer portion of this organ to its union with the 

 oviduct just after the entrance of the latter into the shell gland. The 

 oviduct then enlarges to form the ootype. On emergence from the shell 

 gland the uterus enlarges to form a large pouch, the receptaculum 

 seminalis uterinum. From this the uterus makes a few short loops and then 

 the long loop, previously mentioned, which separates the testes. From 

 this point forward it lies in more or less regular transverse folds which 

 extend out to the vitellaria, tho in some instances, particularly in the 

 posterior three-fifths of the body, these loops extend to the body wall. 

 In the anterior fifth of the body the uterine loops are not so long and 

 here fill out entirely the space between the intestinal crura. From the 



