42 ILLINOIS BIOLOGICAL MONOGRAPHS [42 



A comparison of the furcocercous larvae with the Schistosomatidae shows 

 the strilcing similarity of the excretory systems of these forms. Looss (1895) 

 finds the system of male and female Schistosoma haematobium alike, altho 

 that of the female may be slightly better developed, due to a minimization 

 of the musculature. The bladder is median, non-muscular, except for a 

 weak sphincter at the pore. It receives the two longitudinals at its antero- 

 lateral reaches. There is no median canal (p. 72). Many of the laterals are 

 dendritic, altho they do not anastomose. Small flame ciha are at the heads 

 of the capillary tubes of 3jit to 4/1 diameter. These flame cells and capil- 

 laries are intra-cellular, and not surrounded by an epithelial lining. 



D. Excretory system of the Parthenitae. Details are given only in ob- 

 servations of Looss (1892:158-161) for the excretory system of young parthe- 

 nitae. The "protonephridia" of Ssinitzin (1911:77-80; PI. 1, Figs. 24, 25), 

 described by him in connection with the birthpore of the redia, have not been 

 proved to have an excretory function. 



According to Looss the excretory sytem both in the sporocyst and redia 

 arises as a paired structure, from which capillaries and flame cells soon arise. 

 The observations of the writer have been confined to the adult sporocyst and 

 redia of the species studied, in which the system is strikingly different from 

 the embryonic condition. In many cases the excretory system consists 

 of a diamond pattern of intercellular channels, without any clue to the former 

 bilateral symmetry. The same amount of modification holds for both sporo- 

 cyst and redia. Even in the holostome redia (Fig. 42) this diamond pattern 

 is found. No flame cells have been found in adult parthenitae. This distinct 

 modification of the excretory system in parthenitae is not surprising in view 

 of the extraordinary degeneration of the animal that has resulted from its 

 endoparasitic habits during its entire life. 



Excretory granules. The excretory granules of the cercaria and parthenita 

 are spheroidal and have the general appearance of glass beads. Their re- 

 fractive index is very high. The size of the concretions is variable in different 

 groups and even in the same individual. As a rule the granules are largest 

 in the monostomes and holostomes. 



Few writers have given consideration to these excretory granules. Thomas 

 (1883:117) says for Fasciola hepatica larvae that "the yellowish granules. . . 

 appear to be excretory products formed within the cells of the sporocyst and 

 then ejected. They are partially soluble in acids, leaving an organic basis. " 

 Looss refers to them as opaque concrement-granules which on first sight throw 

 the boundaries of the tubules into black rehef (1894:165). They are insoluble 

 in alcohol and color beautifully in stained mounts. Reference is made to 

 these granules by Cort (1915:16) to the effect that the tubules of the mono- 

 stomes are filled thruout their entire length "with small round concretions 

 which disappear in the process of preservation. " The writer has found that 

 these granules are not usually preserved in the corrosive-acetic fixing fluids. 

 However, if fixation is done without the acid fraction of the fluid the granules 



