228 Henry LEsLIE Osporn, 
versely to the left side beneath the intestine, then with a winding 
course forward remaining mostly or wholly on the left side. It 
runs obliquely dorsally through the diaphragm and then runs to 
the genital pore, where it opens to the exterior. The part of the 
oviduct next the tuba for a short distance is ciliated, but the 
remainder of the passage is not. It is lined everywhere with 
nucleated cells which are clear, tall and strongly nucleated where 
the tube is not cilated, but in the dilated portions which contain 
the eges the wall is of greatly flattened cells whose nuclei are 
elongate. In the beginning of the uterus muscle fibers do not appear 
to be numerous if they are present at all, but in most of the passage 
they are very evident and in two distinct sets circular and longi- 
tudinal. The passage is slightly longer than the body, and hence 
is somewhat coiled, but not extensively as in many trematodes. It 
ends at the genital opening where it always comes in from the left 
opposite to the position of the cirrus sack. In this terminal portion 
of the uterus (metraterm) the epithelium gradually passes into a cuticle, 
continuous with that of the outer surface at the genital opening. 
There is no seminal receptacle. LAURER’S canal is entirely absent. 
It is quite various in Aspidobothridae; absent in Stichocotyle; rudi- 
mentary, ending blindly in Aspidogaster conchicola; present and opens 
dorsally over the testis in Lophotaspis vallei (Looss, 1902); absent in 
Cotylogaster michaelis; present in C. occidentalis and opens to the 
exterior in common with the excretory system; present in Macraspis. 
The vitellaria (Fig. 5) are confined to the hind part of the body 
and entirely underlie the diaphragm (unlike Aspidogaster where they 
are wholly dorsal to it). The number of follicles, in eight individuals, 
was 70, 72, 76, 80, 90, 105, 110. The ducts leading from the follicles 
are ordinarily invisible, but can be demonstrated by making the 
yolk cells flow in them by pressure. They lead to a right and left 
main duct, which enter the yolk receptacle just in front of the 
spermary. The follicles themselves (Fig. 55) measure from 0.05 to 
0.08 mm in width and 0.08 to 0.13 mm in greatest length. Those of 
a particular animal are all of nearly the same size; possibly their 
difference of size in different animals is due to functional conditions, 
but the cells in all have the same appearance. The follicles are 
bounded by an extremely delicate structureless wall, enclosing a 
number of yolk cells in various stages of growth. The smallest and 
earliest cells (Fig. 56) have a diameter of 0.01 mm and bear con- 
siderable resemblance to the youngest ova, having a large nucleus 
