IO6 W. M. SMALLV.'OOL). 



very similar. The testes are usually somewhat larger than the 

 ovaries and contain more cells. They are located in the sixth 

 post-cephalic somite. Frequently the cells in the testis are pear- 

 shaped as contrasted with the spherical form of the young ova. 



FIG. 2. A photograph of Branchiobdella pitlchcrriiua showing the post-cephalic 

 segments, the digestive tube and ganglionic swellings. In the sixth post-cephalic 

 segment the two testes are on one side and in the seventh the ovary shows. 



No evidence was observed to show that nutritive bodies such as 

 Voigt reports for B. varians were present in the cytoplasm ; nor 

 is there a special nutritive cell as in the case of the ovary. In 

 Branchiobdella pitlclicrrima the two testes were found on the 

 same side in one animal (Fig. 2). 



Associated with the formation of the male sex cells from the 

 time they leave the testes until the spermatozoon becomes fully 

 grown there is a protoplasmic structure, termed the blastophore 

 (Bloomfielcl, 'So, Calkins, '95) in Lnmbricus, and the cytophore 

 (Voigt, '85) in Branchiobdella varians. These two terms seem 

 to refer to the same structure and the more recent term, blasto- 

 phore, will be used in this paper. 



Calkins traces the formation of the blastophore and finds that 

 it appears before the sperm cells leave the testis. While still in 

 the testis he figures the blastophore as consisting of eight nuclei 

 in an undifferentiated protoplasm. Repeated division of the nu- 

 cleus unaccompanied by the formation of cells gives rise to a 

 multinucleate cell. After a time " cytoplasmic cleavage occurs 



