4 COMPARATIVE ANATOMY 



movement like that of a flame; hence the name flame-cell. 

 One of these structures, when examined with a high power 

 of the microscope, has a stellate appearance, due to the 

 presence of numerous radiating processes which are said to 

 be exceedingly fine capillary tubes passing from one vesicle to 

 another, and not, as was once thought, protoplasmic processes. 

 The actual number of flame-cells has not been accurately 



c. 



A. The digestive and nervous systems of a mature liver-fluke. The branched 

 alimentary canal is represented in black. C.G, cerebral ganglion ; M, mouth ; 

 V.S, ventral sucker. B. The generative, and C the excretory, systems of the same 

 animal. Ex.p, excretory pore; G.O, genital aperture; Ov, ovary; SJi.-g, shell- 

 gland ; T. T, the ramified testis ; Ut, uterus ; V.G, vitelline glands. D. Enlarged 

 view of the genital aperture and the organs connected with it. Ve. vesicula 

 seminalis; F, vagina ; De, ductus ejaculatorius, Ch, cirrhus ; f, female aperture. 

 (After Sommer.) 



determined for Distomum hepaticum, but they appear to be fairly 

 regularly and symmetrically distributed along each side of the 

 body. In D. volvens thirty-nine flame-cells have been counted 

 on one side of the body. The generative organs are very com- 

 plex, and occupy a large part of the animal's body (fig. i, B). 

 The male organs consist of a pair of much-branched testes, 



