356 University of California Publications in Zoology [Vol.19 



the cercaria, which he believes to belong to Echinostoma revolution 

 (=Distomum echinatum) . This cercaria, however, is not the cercaria 

 of Echinostoma revolutum, as will be proved under the discussion of 

 the adult. The smaller tubules and capillaries as well as the large 

 tubules, divisions of the bladder and excretory pores, correspond with 

 the cercaria of Echinostoma revolutum. The posterior part of the 

 excretory system he fails to show in detail. This failure can now 

 readily be understood because of the cramped condition of the tubules 

 and the density of the cystogenous glands. The anterior arrangement 

 of the tubes of the bladder is nearly the same as in the cercaria of 

 Echinostoma revolutum. The only difference is that at the anterior 

 end the triangular arrangement of the tubes of the bladder as they 

 bend to proceed posteriorly is not present in Looss' form. Lebour 

 (1912, pi. XXVIII) shows three cercariae in which the several divi- 

 sions of the bladder, as far as worked out, resemble the bladder of the 

 cercaria of Echinostoma revolutum. 



Faust (1917 and 1918) describes four new species of echinostome 

 cercariae, Cercariae trisolenata, Cercaria biflcxa, Cercaria chisolenata, 

 and Cercaria acanthostoma. He figures parts of the excretory system 

 of each of these species but in no one does he find a definite pattern 

 for the collecting tubules, accessory collecting tubules, capillaries, and 

 flame cells. Even the part which I have called the complete bladder lie 

 has described very differently in his forms. 



The excretory system of the digenetic trematode is quite conserva- 

 tive. "Wherever the excretory system for different members of the same 

 family has been worked out a marked uniformity is found. Looss 

 (1894, pi. VIII. figs. 157 nad 163) found two distomes, Opisth oglyph e 

 ranae (Froelich) and Eaplometra cylindriacea (Zeder), which belong 

 to the same family, built on the "2 x 6 x 3" plan. Cort (1917) found 

 four fork-tailed cercariae. Cercaria douthitti, Cercaria emarginatae, 

 Cercaria douglasi, and Schistosoma japonicum, with the flame cells 

 arising singly. Since the echinostome family is so uniform in regard 

 to other characters, it seems very improbable that such a conservative 

 system as the excretory should vary greatly. The echinostome excre- 

 tory systems described by Faust are almost entirely different, from 

 those described by Looss (1894), Lebour (1912), and Cort (1915), 

 and from that of Echinostoma revolutum. Faust makes the following 

 statement concerning the excretory system of echinostomes : "This 

 family of distomes is characterized by simplicity of detail in the 

 excretory system except at the head of the main lateral vessel." From 



