Vol. XVIII. December, igog. No. 7, 



BIOLOGICAL BULLETIN 



THE OOGENESIS AND EARLY DEVELOPMENT OF 



HYDRA.^ 



RALPH E. WAGER. 



During the winter of 1904-05 the writer took up the problem 

 of the oogenesis of Hydra, especial attention being given to the 

 cytological changes involved in the development of the &^%. 

 The species upon which the work was done was judged to be 

 H. grisea. The animals were found growing in large numbers 

 in a pond near Syracuse, N. Y. The results obtained were 

 sufficiently marked to warrant publication, but the paper has 

 been withheld until some of the points involved might receive 

 confirmation from new material. 



In the meantime there have been published two papers bear- 

 ing upon the same subject : one by Tannreuther('o8) and another 

 by Downing ('08). In general agreement with the results ob- 

 tained by these two as well as by previous writers, were my own, 

 but in some important particulars they differ widely. For several 

 months past an abundance of sexually reproducing Hydra have 

 been kept growing in the laboratory, and material taken there- 

 from has afforded ready confirmation of the results previously 

 obtained. These results have been reviewed, and, considerably 

 abbreviated, are here presented essentially unchanged. Some 

 discussion of points suggested in recent papers has been inserted, 

 and those particulars in which agreement with other workers 

 exists have been but slightly dwelt upon. 



As above stated, Hydras have been kept growing in the labo- 

 ratory. Observations on these animals yielded interesting 

 results. Early in October, 1907, collections were made from a 

 small stream near Potsdam, N. Y., and the animals brought 



^ Contributions from the Zoological Laboratory, Syracuse University. 



I 



