ART. 9. A NEW TREMATODE FROM WHITE BASS VAN CLEAVE. 5 



tine the crura of which extend posteriorly to within a short distance 

 from the posterior extremity of the body. Ovary a lobed band across 

 the body posterior to the acetabulum and laterally reaching a posi- 

 tion slightly beyond the intestinal crura. Testes rounded or slightly 

 elongated, from 80 to ISOj;. in diameter. Vitellaria surrounding the 

 intestine and extending forward from the ovary to a short distance 

 posterior to the pharynx; on dorsal surface scattered over entire 

 intercecal field. Eeceptaculum seminis located laterally between the 

 acetabulum and the ovary. Seminal vesicle a coiled tube near the 

 median plane about midway between the acetabulum and the 

 pharynx. Uterus heavily massed in posterior region of body and 

 extending forward to the anterior margin of the testes, filled with 

 eggs about 18[x in diameter. Development unknown. 



Type host. — Roccus chrysops (Rafinesque) from Mississippi River 

 and tributary lakes, also from same host at Sandusky, Ohio. 



Type.—Q^t. No. 7634, U.S.M.M.; paratypes Cat. No. 7635, 

 U.S.N.M. and in the collection of the writer at Urbana, Illinois. 



Variability. — Within this species variations in shape and size are 

 so pronounced that it becomes difficult to appreciate the fact that in 

 other trematodes size and general body form must be relatively more 

 stable. Investigators have frequently based contentions for specific 

 distinctions upon characters which observations of living specimens 

 have demonstrated to be very highly modifiable in the individuals 

 of .4. varius. In this species contraction and extension of different 

 parts of the body seem to be subject to distinctly localized control, 

 for almost any part of the body may be in a state of contraction or of 

 extension regardless of the state of its adjoining parts. The results 

 of such uncorrelated actions of the body are shown in the typical 

 instances given in figure 1 (A to G). In the varying states of con- 

 traction of the individual there is usually a slight constriction of the 

 lateral margins in the region of the acetabulum and genital orifice, 

 but in f ull}^ extended individuals this constriction is less marked. 



The influence of contraction of the body seems to be manifest even 

 in the arrangement of some of the internal organs. The testes in a 

 contracted specimen lie almost purely lateral in position (fig. 1, 

 I) and K). In slightly less contracted individuals they lie obliquely 

 in the body (A and C) and in some extreme instances (B) one is 

 almost directl}^ posterior to the other. The possibility of the mechani- 

 cal pressure of the gravid uterus crowding the testes into the lateral 

 position might be suggested. In a number of instances immature 

 individuals in which no eggs were yet accumulated in the uterus 

 (pi. 1, fig. 6) shows the testes in distinctly lateral position. 



The entire oral region is conspicuously modifiable even in the same 

 individual. Figures 3, 4, and 5 show some of the typical views of this 



