A NEW SPECIES OF AVIAN TAPE-WORM. 151 



Description of Genital Segments. 



ISTo sign of the formation of the genitalia can be traced until 

 the fifteenth segment from the neck in each of my specimens ; 

 this was a fixed number. Then, in this segment there appears a 

 triple aggregation of detached cells, somewhat pigmented, which 

 in the following segments are evolved into the three orbicular 

 testes. The cirrus with its pouch and bursa copulatrix is in this 

 segment imperfectly developed, and in the anterior distal dorsal 

 corner is to be seen the wrinkled outline of a cuticular sac which 

 in the succeeding segment becomes the vesicula seminalis 

 exterior. In this segment the male organ of copulation with 

 the female vagina in the same sinus and vaginal canal are 

 perfected ; the testes, having completed their functions by filling 

 the vesicula seminalis exterior, are in the initial stage of 

 absorption, and that organ has passed the sperm on to the 

 vesicula seminalis interior within the bursa. The receptaculum 

 is hanging diagonally empty at the end of the vaginal canal, 

 and thus this proglottis may be looked upon as the perfected 

 hermaphrodite segment, because in the next segment coition has 

 taken place. The vesicula seminalis exterior is a shrivelled, 

 empty sac, the testes have disappeared dorsally, the duplex 

 semilunar ovaries have taken their place ventrally-transversely 

 in the segment, the globular yolk-gland lying between them 

 dorso- vent rally, and in close proximity is the shell-gland. In 

 the ante-penultimate segment, with the exception of the recepta- 

 culum seminis, the organs of generation, if not totally obliterated, 

 are but faintly visible, and what was originally the ovaries for 

 nothing of a uterine canal can be traced has now resolved 

 itself into a somewhat v-shaped uterus, with the ductus 

 efferens of the receptaculum seminis attached to the utero- 

 ovarian membrane. In the penultimate segment the recepta- 

 culum has disappeared, the ovaries have become a closed 

 V-shaped uterus. Here the impregnated ova are not ripe, but in 

 the ultimate or terminal segment have become so i.e. the embryo 

 is a perfect hexacanth or six-hooked brood, ready for transmission 

 to its intermediate host. These transitions are shown in the seven 

 segments, Fig. 5, and are an enlargement of Fig. 1, which is a 

 perfect worm that is, it has not shed any of its segments. 



