76 INVERTEBRATE ZOOLOGY 



end of the body, the uterus is so distended with eggs that most 

 of the other genital organs are obliterated and do not appear. 

 A pair of longitudinal excretory canals passes from one end of 

 the worm to the other, running near and parallel with its two 

 lateral edges and connected in each proglottis by a transverse 

 canal. One or more pairs of longitudinal nerves run parallel with 

 and very near the excretory canals, which are also joined in 

 each proglottis by a transverse commissure. 



Cut off two or three proglottides from the forward end of the 

 body, the same number about a third of the distance from the 

 anterior end, and also from the posterior end, and soak them 

 all first for a short time in a solution of caustic potash and 

 then in one of equal parts of glycerine and water. 



Place the proglottides from the hinder end of the body in 

 dilute glycerine between two glass slides, press them gently so 

 as to 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 proglottis notice a slight pro- 

 jection 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 towards the center of the pro- 

 glottis. These are the vas deferens and the vagina, the former 

 being the larger of the two. The greater part of the proglottis 

 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 proglottis will be seen 

 a straight white band. These are the excretory canals ; find the 

 transverse canal near the hinder end of the proglottis. Between 

 each canal and the edge of the proglottis will be seen a delicate 

 line running parallel with the canal. These are the main 

 nerves ; they are joined by transverse nerves. 



Exercise 4. Draw the proglottis showing accurately all of these 

 features you have observed. 



