A TAPEWORM 67 



squeeze them as thin as possible without crushing them, and 

 study them under the microscope. In the middle of one of the 

 lateral edges of the proglottid notice a slight projection containing 

 a depression. This is the genital papilla, and the depression is the 

 genital cloaca. Two canals will be seen running from the genital 

 cloaca toward the center of the proglottid. These are the vasa 

 deferens and the vagina, the former being the larger of the two. 

 The greater part of the proglottid will be seen to be occupied 

 by a much-branched organ filled with a granular substance. This 

 is the uterus, and the granules are eggs. Near each lateral edge of 

 the proglottid will be seen a straight band. These two bands are 

 the dorsal excretory canals ; find the transverse canal near the 

 hinder end of the proglottid. Between each canal and the edge 

 of the proglottid will be seen a delicate line running parallel with 

 the canal. These are the main nerves ; they are joined by trans- 

 verse nerves. 



Exercise 4. Draw the proglottid, showing accurately all the features 

 that you have observed. 



Study in the same way the mature proglottids. Find the 

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

 proglottid, and is not yet distended with eggs. Near the center 

 and toward the posterior end of the proglottid will be seen an ir- 

 regular 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 proglottid ; 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 throughout the proglottid 

 are numerous small, round bodies, the testes, which are joined 

 with the vas deferens by numerous minute vasa efiferentia. Find 

 the excretory canals and the longitudinal nerves. 



Exercise 5. Draw the proglottid, showing all the features you have 

 observed ; carefully label all. 



Study in the same way the immature proglottids. 



Exercise 6. Draw the immature proglottid, 



