lo Lazelle B. Stnrdevant 



the right or left side of the rostelkim uniting to form a dorsoven- 

 tral loop. Two similar dorsoventral loops within the rostelkim 

 have also been described by Ransom, but are hard to demon- 

 strate in my specimen. These canals are all circular in cross- 

 section, but in the specimen at hand the ventral and dorsal canals 

 appear to be greatly compressed in the dorsoventral direction, 

 giving the large or ventral canals a spindle-shaped cross-section. 

 This is caused by the unusual contraction of the dorsoventral 

 muscular fibers, already mentioned. The appearance of the 

 transverse canals in figure 6 is due to their undulating course, 

 which hence occasionally gives them a dumb-bell outline in 

 section. 



The male organs of reproduction consist of testes, vasa efifer- 

 entia, vas deferens, seminal vesicle, cirrus pouch, and cirrus. The 

 testes are regularly three in number, occasionally two (fig. 4) or 

 four (figs. 3, 8), oval or discoidal or even globular in shape, de- 

 pending on the proportionate contraction of longitudinal, trans- 

 verse, and dorsoventral muscular fibers. In toto mounts the 

 testes most frequently measure 93 /i. long and 120 p. wide, although 

 they are occasionally found 107 /a long by 93 /x, wide. The usual 

 position of the testes is in a row across the proglottid (figs. 3-9), 

 one being on the left side of the ovary, the other two being on 

 the right. When but two testes are present they are found one 

 on either side of the ovary (fig. 4). When four are present one 

 is found to the left, the other three to the right (figs. 3, 8). An 

 unusual arrangement which Grassi has figured, where two testes 

 are found to the left and one to the right of the ovary I have 

 shown in figure 7. Another very exceptional arrangement of the 

 three testes shows them all on the right side of the ovary (fig. 

 9). In one proglottid in figure 4, the testes are not found in a 

 row, but two to the right of the ovary are one behind the other 

 almost in a longitudinal axis. 



From the dorsal side of the testes, arise the vasa efferentia. one 

 from each, and converge toward the median axis of the worm, 

 where they unite to form the vas deferens, which proceeds to- 

 ward the left margin of the proglottid lying close to its anterior 

 border. After the vas deferens has passed the isolated testis, it 



144 



