12 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 55. 



In mature segments it attains a length of 430 to 475 [x and a maxi- 

 mum diameter around 70 [x; in gravid segments the cirrus pouch 

 shortens and thickens, its length being 300 to 345 [jl and its maxinmm 

 diameter about 85 ^. 



Female genitalia (fig. 5). — The ovaries are compact, circular in 

 outline, the one on the pore side being smaller than the one on the 

 aporal side. The vitellarium is elongated along the transverse axis 



of the worm, stains very densely, 

 and is very conspicuous; it is in 

 contact vs^ith the posterior curva- 

 ture of the ovaries and extends 

 across the posterior portion of the 

 interovarian field; it does not ex- 

 tend as far laterally as do the ova- 

 ries. The shell-gland is inconspicu- 

 ous and appears to be commonly ob- 

 scured by either the ovaries or the 

 vitellarium. Near its union with 

 the genital sinus, the vagina com- 

 monly presents a curve or even a 

 conspicuous loop toward the poste- 

 rior portion of the segment, and at 

 this point the vagina is encircled by 

 a well- developed sphincter. From 

 here the vagina parallels the course 

 of the cirrus pouch and the vas de- 

 ferens and then curves around the 

 nearest ovary to the interovarian 

 field. Even in the mature seg- 

 ments the median stem of the ute- 

 rus begins the formation of two 

 lateral branches, one on each side, 

 at the anterior end of the segment. 

 As these develop, other branches 

 form behind them, the new 

 branches being added posteriorly 

 until they invade the region of the 

 ovaries and obliterate them. The lateral branches are notably parallel 

 to one another along the transverse axis of the strobila and show com- 

 paratively little tendency to subdivide, but rather a tendency to be- 

 come sacculate at the distal extremities, so that the segment becomes 

 j&lled with eggs, not as the result of the formation of numerous 

 branches and the anastomosis of these branches, but as the result of 

 the sacculation of the main lateral branches and especially of their 

 distal extremities (fig. 6). The eggs are spherical and 31 to 37 n in 

 diameter. 



'|/iomm.' 



Fig. 6.— Taenia taeniaeformis. Gravid 



SEGMENT. 



