No. 6.] THE CESTODE MONIEZIA EXPANSA. 281 



At the left of b peculiar conditions appear. Besides the 

 organs (b') in the normal position there is another partial set 

 (b") lying to the right of the first. The first set, although nor- 

 mally placed, is imperfect, for the ovary and vitellarium are 

 rather smaller and less branched than usual ; the oviduct, 

 atrium, and pore are normal, but the vas deferens is not com- 

 plete. Its inner end appears anterior to the ovary --near the 

 letter b' - - but it ends blindly posterior to the oviduct instead 

 of in its normal position anterior to it. A peculiar condition 

 appears in five or six of the testes (t t) near the edge. They 

 are enlarged and packed full of spermatozoa, so that they stain 

 like the vas deferens of this stage and are quite different in 

 appearance from the other testes, though the testis cells can be 

 distinguished in them with high powers. The inner portion of 

 the vas deferens is also full of spermatozoa, but the seminal 

 receptacle is empty, indicating that there is no outlet for the 

 sperm into the female organs. In the normal organs of adja- 

 cent segments impregnation has already occurred. The accu- 

 mulation of sperm in the testes (/ /) is doubtless due to the 

 imperfect development of the male ducts. The movement of 

 the spermatozoa from the middle regions of the segment toward 

 the edges having occurred as far as possible-- the testes in the 

 middle region are empty of sperm - - they have accumulated in 

 a number of testes near the edge and remain there, since there 

 is no outlet to the exterior or to the female organs. This con- 

 dition is found in one other case (Fig. 39). 



The small size and imperfect development of the set of 

 organs // is probably clue to the fact that the left half of the 

 segment b is considerably shorter than the normal. The nor- 

 mal length at this age is about that of a, and this portion of b 

 is only a little more than half as wide as a. At the right b is 

 wider and normal organs occur. 



The second set of organs (b"} is very small and rudimentary, 

 consisting of a small simple ovary (0} and two small groups 

 of cells representing the vitellarium (vf) without any traces of 

 ducts. The orientation of these organs in the proglottid is 

 apparently normal. 



This transverse duplication of the female organs does not 



