292 University of California Publications in Zoology [Vol.19 



of the capillary groups and in the length of the accessory collecting 

 tubes of the posterior collecting tubes. These differences are related 

 to the differences in length of the post-acetabular region in the two 

 forms. In other characters the excretory systems of these two species 

 are exactly alike. They correspond in the arrangement of the common 

 and anterior and posterior collecting tubes, in the number and arrange- 

 ment of the accessory collecting tubes and the capillary groups, and 

 finally in the number of flame cells in each group and in the grouping 

 of the capillaries of each group into a 2-1 arrangement as explained 

 in the description of the excretory system of Margeana calif 'or w< nsis. 

 The agreement of the excretory system of Opisthioglyplic raitac 

 (=Distomwm cndolobuni Dujardin) (Looss, 1894, 87, pi. VIII, fig. 

 157) with the two just described is almost as striking. Here the 

 "2-6-3" grouping is carried out exactly as before. The only differ- 

 ence is to be found in the more characteristic Y-shape of the bladder, 

 the divided lobes being almost as long as the main stem. The point 

 where the anterior and posterior collecting tubes meet the common 

 collecting tube in this species is still further back, being at the 

 posterior limit of the second third of the body. This of course makes 

 a difference in the position of the accessory collecting tubes and the 

 capillary groups. 



Anchitrema sanguineum (Looss, 1896, p. 110, pi. 8, fig. 77) the 

 third species with the "2-6-3" type of excretory system has a bladder 

 in which the divisions are equal to the main stem and the points of 

 bifurcation of the collecting tubes are at the level of the ventral 

 sucker just in front of the middle of the body. There are also slight 

 differences in the position and length of the accessory collecting 

 tubes. The three grouping of the capillaries is carried out in this 

 species except in the anterior and posterior groups on each side which 

 have only two capillaries. This makes four capillary groups of two 

 each and eight of the regular three. This difference is easy to under- 

 stand when we consider that in each three group of capillaries the 

 end of the accessory collecting tube is divided into two branches, one 

 of which is directly connected with a flame cell and the other of which 

 divides into two capillaries with flame cells. It is evident that the 

 fundamental pattern of the excretory system of Anchitrema san- 

 guineum is the same as that of the other forms just described, but that 

 the anterior and posterior capillary groups in this form have lagged 

 behind in division (Cort, 1919). 



