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 Russia 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 
Fic. 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. Ligula 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, i some other species this phenomenon is brought 
