Vo/. XV. July, igoS. No. 2 



BIOLOGICAL BULLETIN 



THE OVOGENESIS OF HYDRA FUSCA — A 

 PRELIMINARY PAPER. 



ELLIOT R. DOWNING, 



Northern State Normal School, Marquette, Mich. 



Kleinenberg in his thesis on hydra, 1872, maintained the fol- 

 lowing twelve points in regard to the formation of the ovary and 

 the growth of the &^^ : 



1. The ovary is formed by a rapid multiplication of the inter- 

 stitial cells at the site of the ovary. 



2. There is evidence in the relative infrequency of the inter- 

 stitial cells, in the territory about the forming ovary, that their 

 accumulation may be, in part, due to migration, though he has 

 no direct evidence of this. 



3. The interstitial cells at the center of the ovary are larger 

 than those at the margin. 



4. The interstitial cells are arranged in rows converging toward 

 the center of the ovary. 



5. The egg appears in the midst of the cells of the ovary where 

 it has likely lain, indistinguishable from the interstitials. 



6. It now comes to be distinct because of its rapidly increasing 

 size and its irregular contour. 



7. Later it becomes amoeboid. 



8. In the early stages of the &^^ granules appear in its sub- 

 stance which are equivalent to the white of the ^g^ (protagon) 

 of the eggs of higher forms. 



9. These disappear and then the &g% gradually fills up with 

 the so-called " Pseudozellen " or yolk granules. 



10. The cells about the ^^^ in the ovary disintegrate to form 

 nutritive material for the &^^. 



