2/0 ELEMENTARY BIOLOGY. [CHAP. 



a. The ripe ova, large round .bodies completely 

 filling the pointed extremity of the saccular 

 ovary. A granular vitellus, a large round ger- 

 minal vesicle and a vitelline membrane will be 

 observed for each. 



p. The immature ova. Work towards the base of 

 the ovary — the ova decrease in size and become 

 more numerous. The younger of them are 

 destitute of a vitelline membrane. Work back 

 towards the attached end, and note graduating 

 into P SiS P does into a — 



y. the germinal epithelium, a solid mass of small 

 undifferentiated cells filling the base of the 

 ovary. 



j. Remove a small portion of a testis of the youngest 

 worm obtainable, crush and examine in eosin under 

 a high power. Note the cells of the germinal epi- 

 theliujn, irregular in shape, each with a large central 

 nucleus and a single nucleolus. 



k. Tease up in a similar manner a small portion of 

 one of the seminal vesicles of an older animal. 

 Treat with acetic acid and magenta — spermatozoa 

 in all stages of development will be seen. Look 

 for the following — 



a. Cells of the germinal epithelium identical with 

 j. They are sometimes to be found only with 

 difficulty. 



yS. The same during the early maturation stages — 

 conspicuous as the predominant mulberry-like 

 masses. Focus to the surface of one of these 

 and work through it. It consists of a large pro- 

 toplasmic body, differentiated — peripherally into 



