104 



ZOOLOGY 



attain a length of nearly ten yards. The head is flattened, 

 and bears two lateral slits ; the genital pores are not on the 

 side, but on one surface of each segment. The male orifice is 

 distinct, and in front of the female, and the uterus has an 

 aperture for the exit of the ova, behind the female orifice 

 through which the spermatozoa are introduced. The asexual 

 stage has been found in certain freshwater fish. This parasite 

 is chiefly met with in Eussia and Central Europe. 



Certain genera, as Amphilina, found in the body-cavity of 

 the Sturgeon, and Amphiptyches in the stomach of the Chimaera, 

 have flat bodies with one anterior sucker. Their embryos are 

 ciliated, and their female reproductive organs closely resemble 



Fig. 71. — Tetrarhynchus. 



A. General view of the worm, x 4. 



B. Head, showing the suckers, proboscides, and excretory canals, x 25. 



C. Portion of a proboscis showing the two forms of hooks, highly magnified. 



All after Pintner. 



those of Trematodes. They are therefore looked upon as con- 

 necting the latter class with the Cestoda. Zigula is another 

 genus in which the segmentation into proglottides does not occur. 

 Although, if the proglottides be not regarded as distinct 

 individuals, there is no alternation of generations in Taenia 

 saginata, in some other species this phenomenon is brought 



