The Hirudinea of Illinois. 517 



twice the length of the posterior, except at the margins, where 

 they are more nearly equal. The sensilhe are very distinct and 

 are all placed very close to the anterior margin of the second 

 annulus which, therefore, in spite of its smaller size, is re- 

 garded as (a2+ad). 



XXVII is irregular and more or less divided into two rings, 

 especially at the margins. The anus cuts into the posterior 

 margin of the somite, which at that point is irregularly lobed. 

 The sensillae are close to the furrows by the side of the anus 

 and the dorso-medians are widely separated. XXVIII is 

 somewhat distinct from the sucker and bounds the anus 

 posteriorly. 



Reproductive Organs. — Two examples were dissected, and 

 the small size of the organs renders it probable that they 

 were taken at a time when these were not in full activity. 

 The internal organs of generation (PI. XLIV., Fig. 17) are 

 very simple. 



But seven pairs of small testes (t) were found at the anterior 

 ends of somites XIV to XX. The very slender vasa deferentia 

 (vd) reach to ganglion XI, where they bend back on them- 

 selves and become almost immediately much enlarged and 

 thrown into several folds (ep, de). This region appears to 

 correspond to both the epididymes and ducti ejaculatorii of 

 Hremopis. The two ducts immediately open together into a 

 small thin- walled bursa, and the bursa communicates with 

 the pit as above described. There is no muscular atrium 

 and no penis. Numerous muscular fibers pass between the 

 ventral integuments in the neighborhood of the pit and the 

 dorsal integuments. Ganglion XII is crowded caudad from 

 its normal position to the posterior end of its somite. 



The female organs (PI. XLIV., Fig. 17, 21) are of the 

 Hirudo type. In the specimens examined they are sym- 

 metrically related to the body axis. The ovaries (ov) are 

 sausage-shaped and each is folded on itself. Separate slender 

 oviducts (ov) lead to an unpaired organ, into the large end of 

 which they open. There is no evident external distinction 

 between glandula albuginea, oviductus communis, and vagina, 

 but the. three together are combined in a slender claviform 



