244 CHILD. [VOL. I. 



it is impossible to determine the exact relations. In the organs 

 at c' the portion of the seminal receptacle which lies between the 

 ovary and the point of union of the male and female ducts is full 

 of spermatozoa, while the outer portion is entirely empty, and this 

 fact renders it certain that an actual union of the ducts with 

 an opening does occur, and shows, too, that self-fertilization 

 occurs as well. 



It is important to note that here in c a vas deferens is formed, 

 while in a, as mentioned above, the male duct is absent. The 

 cause of this difference is indicated by the different direction of 

 the partial furrows in the two cases. The partial furrows between 

 a and b at the right extend obliquely backward posteriorly from 

 without inward, and cut off from the segment a the region where 

 the vas deferens would normally form, while the ventral furrow and 

 the dorsal depression between c and d slant anteriorly, and thus 

 a space is left in c anterior to the ovary where the vas deferens 

 may form. The fact that the vas deferens opens into the seminal 

 receptacle instead of extending to the pore, while the oviduct 

 pursues a more nearly normal course, is perhaps not explicable 

 on the basis of the form relations of the segments, but the sug- 

 gestion offers itself that the close approximation of the two sets 

 of organs, c and d, prevents its formation between them where it 

 would naturally appear ; so that it is confined wholly to the inner 

 genital region. The oviduct of c 1 crosses the furrow to reach the 

 pore instead of opening in its own segment. This is probably 

 due to the fact that the degree of separation between the two seg- 

 ments is less than normal ; for, as mentioned above, there is no dis- 

 tinct furrow on the dorsal surface, though ventrally the segments 

 are sufficiently separated to give rise to separate ovaries. No 

 pore at all is found at the right edge of c, and this is probably 

 due to the same fact, vis., that dorsally the degree of division is 

 very slight, so that only one pore is formed for the two segments, 

 though the position of this is apparently affected in some degree 

 by the partial division which does exist, since it is placed some- 

 what anterior to the middle of the edge of c d. 



In the genital organs d' of </ relations are almost normal, but 

 the oviduct is shorter than in c', and the ovary is thus nearer the 

 edge of the proglottid. The oblique direction of the partial fur- 



