40 



PARASITES OF MAN 



formed by the narrowing and bending inwards of the lateral 

 borders of the animal, the right side being more or less com- 

 pletely overlapped by the left margin of the body; caudal 

 extremity pointed ; intestine in the form of two simple blind 

 canals. Female with a cylindrical body measuring only ^ of 

 an inch in thickness in front of the oral sucker; lodged in the 

 gynascophoric canal of the male during the copulatory act ; 

 thickness of the body below the ventral acetabulum being about 

 jjy", and at the lower part 55"; surface almost smooth through- 

 out ; intestinal canals reunited after a short separation to form 

 a broad, central, spirally twisted tube extending down the 

 middle of the body ; vitelligene and germigene canals combining 

 to form a simple oviducal canal, which is continued into a 

 simple uterine tube, finally opening near the lower margin of 

 the ventral sucker ; eggs pointed at one end, or furnished with 

 a projecting spine near the hinder pole. 



The study of the structure and formation of the contents of 

 the ova possesses great interest. When fully developed the 

 eggs are oval, measuring from ~g" to jj^" in length, with an 

 average transverse diameter of j^". Some are a trifle larger, 

 others smaller. Occasionally one encounters narrow specimens, 

 and also aberrant forms presenting a pear-shaped outline. I 

 have met with eggs not exceeding ~" in their long diameter, 

 and xfi" transversely, whose yolk-contents had already arrived at 

 an advanced stage of segmentation. 



The shell is transparent, of a brown colour, and free from any 



markings, lines, or sculptur- 

 ing. One pole of the shell is 

 invariably narrower than the 

 other, and usually presents a 

 more or less pointed extremity 

 (fig. 8). This narrow end 

 commonly displays a sharp, 

 projecting, beak-like spine, 

 which, at its base, constantly 

 rests upon the centre of the 

 pole of the shell, but occa- 

 sionally it is eccentrically 



Fro. 8. Two eggs of Bllharzia. a. With the yolk J J 



coarsely segmented ; *, with the yolk granulated "and placed (fifiT. 8 d). In SOme few 

 the spine wanting. Original. 



examples the spine is re- 

 moved to a little distance from the actual extremity of the 

 shell ; but even in these instances, so far as my observations go, 



