56 PLATYHELMINTHES. 



1. On one side of the proglottid the lateral genital aperture 

 will be seen. The penis is a long, slender organ, found pro- 

 truding, or lying in its sheath near the lateral aperture. The 

 vas deferens, a long, convoluted, tube, extends from the penis 

 to the testes, which form many rounded, deeply stained struc- 

 tures that lie about the oval outline of the uterus. On leaving 

 the penis the vas deferens extends toward the pointed end of 

 the proglottid, along the side of the uterus, until it reaches a 

 point anterior to it, where it may sometimes be seen sending 

 branches to the testes, but is frequently lost. Throughout its 

 length it is greatly convoluted and is generally filled with sper- 

 matozoa. 



2. At the base of the penis, in the lateral genital aperture, 

 is the external opening of the female organs. From this point 

 a small tube, the vagina, leads to a point below the sac-like 

 uterus, which is sometimes very large and sometimes collapsed 

 and small. The vagina ends in a small pouch, the ootype, from 

 which a short canal (sometimes visible, but more often obscured 

 by the vagina, which lies above or below it) leads to the uterus. 



3. The ovary consists of a large many-fingered mass in a 

 median position, near the posterior end of the proglottid. It 

 surrounds, more or less completely, the inner end of the vagina 

 and ootype. 



4. The vitellaria occupy the posterior corners of the pro- 

 glottid, and may extend anteriorly along its margins, by the 

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

 from the vitellaria 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. 



Understand the relation of the ducts of the shell glands, 

 vitellaria, and 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? 



Drau) a figure of the proglottid showing all of the parts you 

 have seen. ' 



