MORPHOLOGY OF CESTODES FROM POULTRY 29 



seminal receptacle (Fig. 16, sr) is a dilation of the vagina into an 

 oval shaped structure which is about SO/x long and from 25 to 30ju, 

 in breadth at the widest part. From the seminal receptacle the 

 vagina passes laterad, lying posterior to the cirrus pouch, and unites 

 with the genital cloaca. The genital cloaca has its pore on the 

 lateral margin near the anterior end of the proglottid. The pore is 

 usually covered by the backward projection of the segment anterior 

 to it. The vas deferens and vagina pass between the dorsal and 

 ventral excretory canals and dorsal to the nerve tract. The vas 

 deferens is dorsal and anterior to the vagina. 



In the mature segments the uterus becomes filled with ova and 

 it increases in size until it occupies the entire area between the 

 excretory canals, even extending beyond the canals in the gravid 

 proglottids. The uterus finally breaks up into compartments, each 

 containing a single embryo. The embryos (Fig. 7) are about 32 

 by 22/i, in diameter with onchospheric hooks 18/x long. Usually 

 three membranes, but often four, enclose the embryo. The inner 

 membrane is thin and closely surrounds the embryo ; the next is 

 heavy, being from 1.5 to 2/i thick, composed of fibrous layers with 

 a few cells present. This layer is variable in thickness, depending 

 considerably upon the amount of contraction of the segment, as it 

 ranges in size from 40 to 32/x to 50 by 26ix, or it may be even 

 slightly larger. Usually one (Fig. 7) and sometimes two thin mem- 

 branes are found on the outside of the thick layer. These are 

 often wrinkled and bear at each end an appendage formed from 

 the outer membrane by which it is attached to the wall of the cap- 

 sule or compartment of the uterus. 



In this species the oldest proglottids drop off from the worm 

 before they are fully m.ature. The embryos from the oldest seg- 

 ments on the worm do not show the characteristics of entirely ma- 

 ture ones, and there are distinct differences between them and those 

 that have been separated from the worm for some time. Single 

 proglottids that have separated from the worm are quite active and 

 remain in the intestine for some time before passing out with the 

 feces. Proof of this is furnished by the fact that a large number 

 of the free proglottids are found in the intestine at any time. Even 

 tho only a few worms are present in the intestine of a bird there is 



