CASTLE : NORTH AMERICAN RHYNCHOBDELLID^. 45 



usually stout and thick in this species and runs forward to the middle ring of 

 somite xi. before turning sharply backward toward the genital pore (compare 

 Figure 19 with Figures 4, 13, 27, and 28). 



The eggs, which in the vicinity of Cambridge are laid in May or June (at 

 about the time G. fusca is laying), are whitish in color and are attached 

 singly, not in groups as in the other species described, to the under side of the 

 body (Figure 22). The eggs are of about the same size as those of G. stagnalis. 

 The number laid varies greatly with the size of the individual, the observed 

 extremes being eleven and sixty-five. Figure 22 shows in ventral view a large 

 individual bearing forty-five eggs, each enclosed in a separate delicate sac 

 which serves to attach it to the under side of the body. 



d. Digestive Tract. 



The mouth has the position most common in the genus, in the anterior part 

 of somite iii. (Figure 20). 



l!}i& proboscis (pr^b., Figure 19) is long and the oesophagus correspondingly 

 short. The former ordinarily extends over somites ix.-xii. and part of xiii., 

 and the latter ends in the anterior part of somite xiv., where the crop com- 

 mences. 



The salivary glands (gl. sal., Figure 19) are large and distributed often 

 through as many as seven or eight somites, usually somites xi.-xvii. 



The crop (I'glv., Figure 19) bears six pairs of strongly developed lateral 

 diverticula, a pair arising in the middle of each of the somites xiv.-xix. 

 Some or all of the first five pairs may be bilobed distally, and each of the 

 sixth pair, which are very long, and extend back into somite xxiii., bears 

 about five secondary, lateral diverticula, which come off metamerically in 

 somites xix.-xxili. 



The stomach (ga., Figure 19), with its four pairs of lateral diverticula, lies 

 within somites xix.-xxii. 



The intestine (in., Figure 19) begins about in somite xxii. and extends back 

 to the anus just behind somite xxvii. Proximally it consists of one or two 

 chambers limited by valve-like constrictions. Posterior to this it gradually 

 narrows backward. 



e. Nervous System. 



The brain (cb., Figure 19) lies about in the eighth somite. The arrange- 

 ment of its ganglionic capsules is peculiar in one respect. The ventral capsules' 

 of the last brain neuromere (Figure 21) lie side by side, not tandem as in 

 the other species described in this paper. In other respects the arrangement 

 of capsules is the same as that found in G. stagnalis and G. fusca (Figures 8, 

 12, 16, 18). In the individual whose brain is represented in Figure 21, the 

 most ventral and posterior capsule of neuromere i. had a horn-like process ex- 

 tending back laterally into contact with the lateral capsules of neuromere iii. ; 

 this condition, however, appears to be unusual. 



