44 PLATYHELMINTHES. 



4. The vitelline glands occupy the posterior corners of the 

 proglottid and may extend anteriorly along its margins, by the 

 sides of the testes, nearly to its anterior extremity. The ducts 

 from the vitelline glands unite and join the ootype. 



5. The shell gland is a small median mass that is situated 

 between the lobes of the ovary around the ootype. 



From the lecture and figures, understand the relation of the 

 ducts of these glands and the vagina to the ootype and uterus, 

 how and where the eggs are fertilized, and how they are finally 

 lodged in the uterus. Why should hermaphroditism occur in 

 this form? 



Draw a figure of the proglottid showing all of the parts you 

 have seen. 



Larval Stage. Examine and draw a specimen of the larva 

 found in the cystic duct of the squeteague. The scolex with 

 its suckers at the anterior end, and the opening of the water- 

 vascular system at the posterior end, are readily seen. Compress 

 slightly if the trunks of the water-vascular system are not easily 

 seen. They can always be seen in preserved and stained speci- 

 mens that have been killed under pressure. If you have trouble 

 in seeing them, examine such a specimen. Do you find pro- 

 glottids? Understand the relation of this larva to a true cysti- 

 cercoid. 



NEMERTINEA. 



Several representatives of this group are rather easily ob- 

 tained. Some of these, as some species of Cerebratulus and 

 Meckelia, are large, but they are generally unsatisfactory for 

 anatomic study, as they are opaque and filled with a connective- 

 tissue parenchyma that binds the organs together. Further- 

 more, they are especially likely to cut themselves into small 

 pieces by contraction of muscles in the body-wall. 



TETRASTEMMA. 



This small animal lives among the forms that are generally 

 found attached to piles. Specimens ran usually be found by plac- 



