OBSERVATIONS ON GERM CELLS OF HYDRA. 2CX) 



viduals with both spermaries and ovaries at the same stage of 

 development were isolated and placed in distilled water for one 

 hour, in order to kill any mature sperm that might adhere from 

 other individuals. The Hydra were then placed separately in 

 water free from sperm. The spermaries and ovaries matured 

 and self-fertilization took place. The cleavage was normal. 



SUMMARY. 



1. Hydra sp. ? (Brauer) does not show continuity of the germ 

 plasm. 



2. The eggs can be distinguished from the interstitial cells in 

 the adult Hydra before the ovary is formed. This is especially 

 true during the breeding season. 



3. The different generations in the formation of the germ cells 

 are comparable to those of higher animals. 



4. In the division of the spermatocytes of the first and second 

 generations the cell wall remains intact and the four spermatids 

 are formed within a common vesicle, each producing a mature 

 sperm. 



5. Self-fertilization occurs in Hydra viridis. 



ZOOLOGICAL LABORATORY, 



UNIVERSITY OF MISSOURI. 



BIBLIOGRAPHY. 



1. Brauer, A. 



'91 Ueber die Entwicklung von Hydra In. Z. f. Wiss., Zool., 52, 2. 



2. Downing, E. R. 



'04 The Spermatogenesis of Hydra. Zool. Jahr., Band 21. 

 '08 The Ovogenesis of Hydra fusca A preliminary paper. Biol. Bulletin, 

 Vol. XV., No. 2. 



3. Hertwig, R. 



'06 Ueber Knospung und Geschlechtentwicklung von Hydra fusca. Biol. 

 Centralbl., Vol. 26. 



4. Kleinenberg, N. 



'72 Eine anatomisch-entwicklungsgeschichtliche, Untersuchung. Leipzig. 



5. Korotneff, A. 



'83 Zur Kentniss der Embryologie der Hydra. Z. Wis. Zool., Bd. 38. 



6. Tannreuther, Geo. W. 



'08 The Development of Hydra. Biol. Bulletin, Vol. XIV., No. 5. 



