24 BULLETIN: MUSEUM OF COMPAKATIVE ZOOLOGY. 



The oral sucker (sue. or.. Figure 7) lies on the ventral side of the head, within 

 the limits of rings 1-3 (somites i.-iv.). 



The mouth {or., Figure 7) opens anterior to the middle of the oral sucker as 

 well as anterior to the eyes. 



The posterior sucker (act, Figures 1, 4), also ventral in position, is slightly 

 longer than broad. Average dimensions for the largest individuals are : — 

 length, 1.31 mm. ; width, 1.24 mm. 



d. Eepkoductive Organs. 



The male genital pore (po. $, Figure 4) lies in a mid-ventral position between 

 rings 24 and 25 ; that is, between the anterior and middle rings of somite xii. 



The female genital pore (po. 9) Figure 4), which is a broad transverse sHt, 

 lies just one ring behind the male pore, between rings 25 and 26, the middle 

 and posterior rings of somite xii.^ 



Testes (Figure 4, te.), six pairs, placed intersegmentally in somites 5-il'_?ZHi'. 



XIV. XIX. 



The size and appearance of the testes vary considerably with the seasons. In 

 the fall and early spring they are generally large and their outlines more or 

 less irregular, for they adapt themselves to the spaces left them among the 

 dorso-ventral muscles and other deep-lpng organs. The testis wall is quite 

 thick on its dorsal, ventral, and lateral aspects, but somewhat thinner on its 

 median aspect. It is lined with a loose germinal epithelium of spindle-shaped 

 cells, except at its dorso-median angle, where there is a small patch of ciliated 

 epithelium continuous with that of the vas eflFerens. 



Male genital ducts. — The vas eiferens is a short, delicate tube, which leads 

 dorsad and cephalad to join a longitudinal duct similar in structure to itself 

 and only slightly larger, the proximal or collecting part of the vas deferens 

 (Figure 4, va. df.). Anterior to the first pair of testes, that is, about on the border 

 between somites xii. and xiii., the collecting portion of the vas deferens bends 

 sharply toward the median plane of the body and passes between the strong 

 dorso-ventral muscles, which, like a row of pillars, mark off on each side the 



1 I am unable to find in any published account an explicit statement as to the 

 position of the genital pores in this species. Budge ('49) figures the male pore in 

 the posterior third of ring 25 and says, " Gegen den 25 Ring findet sich die sehr 

 feine mannliclie Geschlechtsilffnung." He does not figure the female pore, but 

 says (p. 100), "Ungefahr am 27. Leibesringe die iiusscre [female] Geschlechtsilff- 

 nung liegt." Tills would make the genital pores distant from each other about two 

 rings, which, however, is incorrect. 



Ludwig ("86) incorrectly describes the position of the genital pores for the 

 entire genus " Clcpsine " as follows (p. 781) "miinnliche Geschlechtsilffnung 

 zwischen dem 25. und 20., wcibliche zwischcn dem 27. und 28. Ringel." This state- 

 ment rests upon two erroneous assumptions, first, that the number of distinct rings 

 is the same in the head region of all species, and, secondly, that the genital pores 

 are always two rings apart. In only two of the six species described in this paper 

 are the genital pores separated liy two rings. 



