251] 



NORTH AMERICAN MONOSTOMES 



33 



left positions are on the whole equal in number and where significant 

 differences occur they are perhaps due to the small number of individuals 

 studied. In Cyclocoelum obscurum with sixty specimens in the lot the 

 difference is relatively small. The total of ninety-four specimens in all 

 show an approximately equal count for each arrangement. 



The variation in the position of the testes from one another is equally 

 of little importance from the standpoint of specific diagnosis. However, 

 since Stossich used this as the means of separation of species in Cyclocoe- 

 lum and Haematotrephus the writer feels it worth while to give here the 

 result of observations on American material. Kossack raised objections 

 to the importance assigned this point by Stossich and showed that the 

 variation within a species was even greater than that between the genera 

 before mentioned. 



The study of the American material has served to substantiate the 

 view of Kossack (1911) reached by study of the European material. 

 Reference to table shows the number of uterine loops to vary from none 

 where the testes lie contiguous to one another to nine while the entire 

 number of uterus loops, counted always on the side of the anterior testis, 

 is likewise variable and appears to bear no relation to the total number of 

 uterine loops between the testes of the individual since the specimen 

 which showed nine loops between the testes has in all only 38 loops while 

 in another individual of the same lot of Cyclocoelum obscurum, which had a 

 total of 40 loops only 3 could be found between the testes. Other examples 

 are 8 and 43; 3 and 44; 7 and 39 as compared to 1 and 39. These are a few 

 examples taken from Cyclocoelum obscurum. Other species show the same 

 to be true except in Cyclocoelum halli and Cyclocoelum triangularum where 

 the relative positions of the genital glands appear to be constant. How- 



