The Ovogenesis of Hydra. 323 



Explanation of Plates. 



Plate 11. 



Fig. 1. Cross-section of Ä dioecia. 58:1. A mature egg at the 

 right ; the section is not through its center. 



Fig. 2. Three oogouia from H. dioecia. 1200: 1. Two of the cells 

 show division stages. The upper egg has a longitudinal diameter of 

 17-7 ^i. 



Fig. 3. Section through a young ovary of H. dioecia. 470 : 1. The 

 figure shows the ectoderm and a pert of the endoderm. Note the position 

 of the nuclei, the fibrous character of the protoplasm at the base of the 

 ectoderm cells, the granular character at the periphery. 



Fig. 4. Section of a part of the wall of H. fiisca. 750 : 1. An 

 oogonium lies between the ectoderm cells. The club shaped cell in the 

 endoderm is a gland cell ; such are conspicuous shortly after the ingestion 

 of food. 



Fig. 5. Ectoderm of H. fiiscn. 750 : 1. Showing two oogonia. 



Fig. 6. Section of the ectoderm and mesogloea of //. dioecia, with 

 an imbedded egg about full-grown. 



Fig. 7. H. fusca. 320: 1. Section through the ovary, parallel to 

 the longitudinal axis of the animal's body and tangentially to its cylindrical 

 surface. The egg, in the amoeboid stage, is shown among the interstitial 

 cells ; those interstitials at the upper part of the figure are undergoing 

 active incorporation by the egg. 



Fig. 8. Margin of a mature egg of H, dioecia. 750:1. Showing 

 the immense nucleus. 



Fig. 9. The nucleus of egg of H. fusca. 7b0 : 1. Drawn at the 

 time of the amoeboid stage. 



Fig. 10. The margin of an ovary of H. dioecia showing aggregation 

 of the interstitial cells. 



