2 RALPH E. WAGER. 



into the laboratory were placed in large gallon aquaria jars. In 

 the jars were several species of unicellular, and sonne more highly 

 organized plants in sufficient quantity to oxygenate the water. 

 A few small pond snails were valuable in keeping the jars clean. 

 In about two or three weeks after collection the animals began 

 to bud very actively, and the dozen or so in each jar soon 

 increased greatly in numbers. In one jar it w^as estimated that 

 there were between two and three hundred individuals. This 

 asexual period lasted between ten days and two weeks when 

 there began an active sexual phase apparently as marked as had 

 been the asexual. Throughout the winter months, and indeed, 

 until observations were discontinued in July, 1908, this alter- 

 nation of asexual and sexual periods was constant. At no time, 

 however, were the reproductive activities entirely of one sort, 

 but that there were periods of greatest sexual and of asexual 

 development there could be no doubt. The ■^ame cultures have 

 been kept under observation during the past year and somewhat 

 similar though less marked conditions have been noted. The 

 long vacation period during which they were without attention 

 brought them to the fall of 1908 in a somewhat depleted condi- 

 tion. With fresh (distilled) water and food they began again to 

 bud and produce eggs and spermaries. Their activities during 

 the past few months, however, have been much less marked 

 than formerly. This, I believe, to have been due in large part 

 to the accumulation in the water of metabolic products dele- 

 terious to the normal activities of the animal. When taken from 

 the jars and placed in fresh water with a plentiful supply of food, 

 they began at once to bud rapidly and after a time to produce 

 both eggs and spermaries, though, it must be said, with a vigor 

 less than when the culture was first started. In proper environ- 

 ment, then, the Hydra will for a long time continue to repro- 

 duce both asexually and sexually, and the maximum develop- 

 ment of each phase occurs in alternating cycles, or periods. 



The embryos developed during the first sexual period were 

 entirely of the flattened, short-spiculated form figured by Korot- 

 neff ('83) and Brauer ('9i«) as that of H.fusca. These same 

 animals, or at least their descendants, thereafter produced only 

 the spherical heavily spiculate embryos figured by Kleinenberg 



