CASTLE; NORTH AMEEICAN RHYNCHOBDELLID.E. 53 



(middle) pair is closely united with sensillse situated in the first ring of so- 

 mite III. (Figure 2), a fact which Whitman ('92) established for " C. hoUensis" 

 and which I can completely confirm for the species under discussion (Figure 2).^ 



Whitman ('92) further established the fact that the anterior pair of eyes 

 in " hollensis " originates in connection with the sensillse of somite ii. He 

 gives no statement as to the origin of the posterior pair. Comparison with G. 

 elegans (Figure 29), however, leads me to regard this pair as probably derived 

 from the sensillse of somite iv. If so, the condition of the eyes in parasitica 

 can be derived in its entirety from that found in G. elegans by supposing that 

 both the anterior and the posterior pairs of eyes have become rudimentary and 

 been brought close to the large middle pair. 



The mouth (or., Figure 2) apparently lies between somites i. and ii. ; in other 

 species it lies farther back, usually in the anterior part of somite ill. The oral 

 sucker is formed by somites i.-iv., as in other species. 



d. Eeproductive Organs. 



The genital pores are situated in this species exactly as in G. elegans ; the 

 male {po. ^, Figure 3 6), between somites xi. and xii. (rings 27 and 28) ; 

 the female (po. 9 )> between the middle and posterior annuli of somite xii. 

 (rings 29 and 30). 



Testes, six pairs situated intersegmentally in somites 1 — 1 _ ^-IIL, the usual 



XIV. XIX. 



position in the genus. 



The eggs are large, white, and opaque. In the vicinity of Cambridge they 

 are laid in May and June, perhaps also in July. In the case of those animals 

 which laid in the laboratory, the eggs appeared to be attached loosely in a sin- 

 gle group of fifty or more to the side of the aquarium, rather than to the body 

 of the leech as is the case in the other species studied. The leech remained 

 closely arched over the eggs, — a position from which it was removed only 

 with great diflBculty. 



e. Digestive Tract. 



The digestive tract resembles very closely that of G. elegans, but has one 

 strikingly distinctive feature : the salivary glands (gl. sal. Figure Sb), instead 

 of being distributed through several somites in the crop region, are closely 

 aggregated into two compact groups in each half of the body, these groups lying 

 symmetrically, a pair on either side of the proboscis, within somites ix.-xi. 



1 On account of this and other close structural agreements tp ith " C. hollensis " 

 as described by Wliitman ('92), I was for some time inclined to regard that name 

 as well as " chelydrae " as a synonym with parasitica, and I have so treated it in a 

 recent publication (Castle, 1900). Professor Whitman, however, has subsequently 

 informed me in a letter that in hollensis " there are several pairs of pigmented eyes 

 behind the pair usually recognized as ' eyes.' These are quite conspicuous in the 

 living leech, and I have never seen any such feature in other Clepsines." This 

 being so, it is probable that hollensis should rank as a distinct species. 



