CASTLE: NORTH AMERICAN RHTNCIIOBDELLIDvE. 



37 



was observed in one case. The number of eggs in a sac, as well as the total 

 niuuber of eggs hiid by iin individual, is greater in this species than in G. stag- 

 nalis. The following figures will indicate the number of eggs borne by four 

 good-sized individuals, which laid eggs in the laboratory in June, 1898. The 

 vertical line represents the median plane of the body; the positions of the 

 numerals show how the sacs were placed with reference to one another and to 

 the median plane of the body ; the numerals themselves indicate how many 

 eggs were in each sac. Anterior is toward the top of the page, and the right 

 skfe of the body toward the left of the page, the animals having been observed 

 in ventral view. 



Individual I. 



Individual II. 



Total 



16 



16 

 22 



17 



20 /. 

 13 



54 + 50 



104 



11 

 15 



18 



6 



13 I 

 14 



44 + 33 = 77 



Individual III. 



Individual IV. 



16 



r. 21 



17 



5 

 14 



19 /. 

 13 



54 + 51 = 105 



Average number of eggs in a sac in above cases, 15 (as against 4 in G. stag- 

 nalis) ; average number of eggs borne by an individual, 94 (as against about 30 

 in the case of G. stagnalis). 



It will be noticed that one of the anterior sacs often contains a relatively 

 small number of eggs (as noticed in the case of G. stagnalis also), suggesting 

 that it served to finish off the egg-laying, the sacs being arranged in the order 

 in which they were formed, from behind forward. 



d. Digestive Tract. 



The mouth is situated anterior to the eyes, well forward in the anterior half 

 of the oral sucker (Figures 14, 15). From here the thin-walled pharyngeal sac 

 {sac. phi/,, Figure 13) leads back to the base of the proboscis in somite xri., just 

 behind the male genital pore. When the animal is at rest the proboscis (pr'b., 

 Figure 13) usually extends through the four somites between the brain and 



