386 E. R. DowxninG. 
Budding, Regeneration and sexual Reproduction. 
During most of the year Hydra reproduces by budding. Only 
for a short time is it reproducing sexually. The processes seem to 
be antagonistic. Certainly they are seldom contemporaneous in the 
same animal. Once I observed a hydra budding in which a nearly 
mature bud had the testes developing. LAURENT records that in 
one instance vigorous budding followed the formation of the ‘tumors’ 
so that he inclined to account for the budding by the irritation 
produced by these pustules, an explanation which is nullified by the 
recognition of these pustules as testes. My observations are that 
sexual reproduction is an exhausting process in Hydra. It is followed 
by vigorous feeding which induces budding. TREMBLEY also observed 
that the process of regeneration was checked by the appearance 
of a bud. Regeneration, budding and sexual reproduction seem then 
to be mutually exclusive — a condition that is likely due to the 
fact that each of these processes primarily utilizes the same cells, 
the interstitials. However the relations of these processes have not 
yet been satisfactorily determined and the subject is one still open 
for observation and experiment. 
Experiments. 
Some experiments have been made in the course of these 
studies with a view to determining under what conditions Hydra 
would reproduce sexually, but thus far only negative results have 
been obtained. 
Changed temperature. 
It was noticed that A. fusca and H. dioecia begin their 
sexual reproduction in the fall and the decreased temperature was 
thought of as the possible occasion. Fifty experiments were con- 
ducted by placing a few Hydra in a dish with water and some plant 
life, imitating natural conditions as closely as possible, and sub- 
jecting them to decreased temperature, for varying times from a few 
hours to a week, and under varying conditions of light and darkness. 
Alternations of heat and cold were also tried. In only one case 
out of the fifty experiments did the sexual organs develop. This 
was on one animal which had been kept in a refrigerator in dark- 
ness at about 12 degrees C. for twelve hours. As there appeared 
at the same time sexual organs on several control Hydra in the 
laboratory which were kept in the light at the temperature of the 
room, it can only be concluded that light and temperature are not 
