A TAPEWORM 77 



Study in the same way the mature proglottides. Find the 

 uterus. It is here a straight, narrow tube in the middle of 

 the proglottis, and is not yet distended with eggs. Near the 

 center and towards the posterior end of the proglottis will be 

 seen an irregular mass of organs. These are the paired ovaries, 

 two large round bodies, one on each side of the uterus; the 

 median yolk gland, which is below the end of the uterus, near 

 the posterior margin of the proglottis ; the shell gland, between 

 the yolk gland and the uterus. From the shell gland the vagina 

 and vas deferens proceed to the genital cloaca, the former being 

 the smaller and more posterior of the two. Scattered through- 

 out the proglottis are numerous small round bodies, the testes, 

 which are joined with the vas deferens by numerous minute 

 vasa efferentia. Find the excretory canals and the longitudinal nerves. 



Exercise 5. Draw the proglottis showing all of these features you 

 have observed; carefully label all. 



Study in the same way the immature proglottides from the 

 forward end of the body. Find as many of the organs men- 

 tioned as are present. 



Exercise 6. Draw the immature proglottis. 



The tapeworm may fertilize itself or be fertilized by another 

 individual, and where self-fertilization takes place one pro- 

 glottis of the animal may fertilize another or a single proglottis 

 may fertilize itself. The ova from the ovaries, on being ferti- 

 lized, pass at once into the uterus. The ripe proglottides, 

 which are filled with eggs in which the embryo has already 

 begun to develop, break off from the hinder end of the worm 

 and pass out of the body of the host. They then break open 

 or are crushed and their eggs are scattered on all sides. 



The encysted tapeworm. The adult worm alone is found in the 

 intestine. The eggs, in order to develop, must pass out of the 

 host and fall upon something which will afterward be eaten by 



