1920] Johnson: Life Cycle of Echinostoma Revolution (Froelich) 357 



my study of the cere-aria of Echinostoma revolution I am inclined to 

 think that just the opposite is true. Certainly the excretory system 

 is very complex in this one species and since it is such a conservative 

 system I can hardly believe the species of the Echinostomidae differ 

 much on fundamental points. I even venture to suggest that when 

 this system is studied in detail in more echinostomes the detailed 

 arrangement of parts will be found to be quite similar in pattern. 



The parts of the excretory system found in the tail of Echinostoma 

 n volutum, although very simple in arrangement, were found hard to 

 work out on account of the deceptive appearance of the muscles in 

 this region. This part of the excretory system of Echinostoma revo- 

 lutum corresponds with the description given by Looss (1894, fig. 191), 

 by Lebour (1912, pi. XXVIII, figs. 9, 13, 17) and by Cort (1915, figs. 

 39 and 43). This makes a total of at least seven echinostomes show- 

 ing the same arrangement of the bladder tubules in the tail of the 

 cercariae. The four echinostome cercariae described by Faust differ 

 decidedly on this characteristic from any of the above. They also 

 differ much from each other. He shows none of them with excretory 

 pores in the tail, and the excretory system in the tail of Cercaria tri- 

 solenata is shown as a single tube. Faust makes the following state- 

 ment in regard to Cercaria biflexa (1917, p. 79) : "The excretory tube 

 in the tail is a single median tube for about two-fifths of the way 

 distad, at which point it forks and continues double the remainder of 

 the way distad, with numerous cross anastomoses. It does not open 

 to the outside either on the sides or end." The excretory system in 

 the tail of Cercaria acanthostonm Faust, finds to be still different, as 

 is shown by the following quotation : ' ' The excretory system in the tail 

 is confined to a long sac-like reservoir, extending the entire length of 

 the organ without any definite wall or lining. Near the proximal end 

 it frequently bulges out on each side to form a lateral reservoir. ' ' He 

 shows this sac-like reservoir in the tail to be fully four times the size 

 of the muscular sac of the bladder. Cercaria chisolenata he finds to 

 be somewhat like Cercaria trisolenata, although the ending of the 

 excretory tube is not quite so definite. I feel quite certain that he 

 confused the tail excretory parts with the tail muscles. This state- 

 ment is borne out by the fact that in Cercaria chisolenata (1918. fig. 9) 

 he shows the tube in the tail and the muscles of the tail with the same 

 type of line and then loses the excretory tube in the muscles. This 

 apparent extension of the excretory tube in the tail as shown in 

 Cercaria chisolen-ata and Cercaria biflexa, I have observed in the 



