1920] Johnson: Life Cycle of Echinostotna Bevolutum (Froelich) 351 



from the same point and drain the region at the posterior end of the 

 acetabulum, while the other set is just a short distance behind, each 

 capillary being attached singly. If the accessory collecting tubule for 

 the first group exists it may be said to be between the capillaries lis 

 and 12x, while the latter group might be said to have for its accessory 

 collecting hibule the part between 13x and 15x. Another collecting 

 tubule (2c), if such can be said to exist, receives a very short accessory 

 collecting tubule (3f), which in turn receives three capillaries almost 

 uniting at the same point. The flame cells in this group are numbers 

 16, 17, and 18 and are located just behind the group previously men- 

 tioned, being about half-way between the acetabulum and the posterior 

 end of the body. The other collecting tubule (2d) is very short. Into 

 it flow the wastes of the accessory collecting tubules (3g and 3h). To 

 the former of these (3g) join capillaries of flame cells 19, 20, and 21; 

 to the latter (3h) capillaries of flame cells 22, 23, and 24. 



Thus the ascending tubes of the bladder (le) are joined on each 

 side by four collecting tubules. One receives three sets of three flame 

 cells each ; two receive two sets each, and one only one set. On each 

 side of the body are twenty-four flame cells. The formula for this 

 system is then "2x8x3," totalling forty-eight flame cells, according to 

 the plan used by Looss (1894, p. 68) and lately adopted by Cort (1919, 

 p. 2). There are no flame cells found in the tail. The anterior half 

 of the body contains only six flame cells on each side, while the pos- 

 terior half has eighteen. In terms of the cercaria this arrangement is 

 hard to explain, but in the light of the adult echinostome the number 

 at either end is quite readily understood. In the adult (fig. 49) the 

 region of the body back of the ventral sucker is several times longer 

 than that anterior to it. Since I believe that the number of flame cells 

 of the cercaria is the same as that of the adult, it is plain that a 

 stretching of his system to meet the adult 's growth at the posterior end 

 would result in a uniform distribution of the flame cells throughout 

 the entire body when the worm is full grown. 



As stated previously, a significant progressive modification of the 

 attachment of the capillaries is noticeable throughout the cercaria. At 

 the posterior end of the body the groups of three capillaries join at a 

 common point on the accessory collecting tubule and form very definite 

 capillary groups. The more anteriorly the capillaries join the more 

 widely separated are the groups on the collecting tubule or its acces- 

 sory. At the anterior end, unless the plan of arrangement of the 

 capillaries into threes were known to exist throughout the rest of the 



