373] AN0PL0CEPHAL1DAZ—D0UTHITT 23 



Perhaps the most striking of these differences is seen in the position 

 of the genital pore. This is explained however when one notes that in 

 the elongate proglottid the portion of the body wall anterior to the 

 genital pore lies much nearer the longitudinal muscles, and more nearly 

 parallel to them, than does the portion posterior. As a consequence the 

 anterior part would be shortened much more than the posterior in the 

 process of contraction. That such is the case is shown by the fact that 

 in contracted specimens the cuticula is much thicker anterior to the 

 pore and is thrown into many fine wrinkles. 



In order to make sure that these were really of the same species, 

 experiments were performed with the object of trying to produce the 

 two types at will. Complete success was attained with the simplest 

 methods of treatment. Living specimens, just removed from the host, 

 were cut each into two pieces; one was placed in a dish of water, the 

 temperature of which was estimated to be about 30° C ,• the other in a 

 dish of about 37°, care being taken that the portions from different 

 worms were not confused. Those in the warmer dish soon expanded, 

 and while in this condition they were fixed in corrosive sublimate. Those 

 in the colder water contracted, however, and could not be induced to 

 expand. When sectioned the portions from warm water were found to 

 be without exception of the type first described, and those from the 

 cold water of the second type. This simple experiment shows the 

 necessity in comparing cestodes of taking into account the state of 

 contraction of the proglottid. 



These descriptions, as already stated, apply to specimens from 

 central Illinois. As one passes northward, however, it is found that the 

 individuals grow steadily smaller, both in bulk and number of proglot- 

 tids. In anatomical features only one difference was discerned: the 

 testes become very regularly fewer; apparently their size remains about 

 the same, tho their irregular shape does not permit of exact determina- 

 tion on this point. The most conspicuous difference between the worms 

 from different localities is in size, those from the north being only about 

 half the length and breadth of those from the south. The other differ- 

 ences are illustrated in the following table. The numbers in parenthe- 

 ses indicate the numbers of individuals or proglottids examined. 



