365] ANOPLOCEPHALIDJE—DOUTHITT 15 



occasional uterus are eggs present. These two individuals have each 

 289 proglottids; in all three cases some proglottids have been shed. 



I can offer no certain explanation of this condition. The genital 

 ducts appear normal and the ova certainly do not pass into any other 

 organ than the uterus. There can hardly be any doubt therefore that 

 these cestodes were incapable of perpetuating themselves. To find the 

 end proglottid, or even several of the terminal proglottids sterile would 

 not be surprising; but to find nearly a hundred such in individuals 

 that have already shed some of their proglottids is certainly not to be 

 expected. Such a condition could of course arise as a mutant, incapable 

 of perpetuating itself; in this case it could hardly be thought to have 

 arisen from Andrya macrocephala, the nearest known relative ; for while 

 these and that species resemble each other in a general way, they differ 

 in nearly every organ. A more probable explanation seems to be that 

 the gopher is not the normal host and that sterility has resulted from 

 unnatural conditions of environment. Sterility as a result of unnatural 

 environment is a very common phenomenon in both animals and plants ; 

 and there is no reason why the condition might not be found in ces- 

 todes. Each of these explanations is favored by the fact that the three 

 individuals were all found in the same host and were of the same size 

 and appearance, making it appear probable that they arose from a 

 single infection. 



The excretory ducts show striking features also. As in A. macro- 

 cephala the ventral ducts are enormously developed. In this case the 

 development is much greater however, especially that of the transverse 

 commissure, so that often the proglottid is nearly separated by the 

 excretory ducts into dorsal and ventral parts, the testes being dorsal 

 and the ovary and uterus ventral. The transverse commissures are 

 frequently three or four times as wide as the space between them ; and 

 when the ventral longitudinal ducts are likewise thus developed, the 

 medullary space within these commissures becomes a mere patch in the 

 anterior part, not much larger than is necessary to contain the vitelline 

 glands and the female ducts. This enormous development is not con- 

 stant however ; such a development as described may be in a proglottid 

 adjacent to one with ventral ducts 60//, in diameter. This is still an 

 unusual size but is not greater than that found regularly in A. macro- 

 cephala. The dorsal duct has a rather sinuous course and is of ordinary 

 size. It lies laterad of the ventral. 



Altho differing in practically every organ from A. macrocephala, 

 there is a fundamental resemblance between these two which argues for 

 generic relationship. The similarity to Anoplocephala in the distribu- 

 tion of testes is interesting but is not to be taken as of more than specific 



