No. 523] REPRODUCTION OF DAPHNIA 407 



Woltereck maintains that Ostwald's results were due 

 to the fact that at a higher temperature the daphnids 

 need more food. Woltereck caused decrease in body 

 length both by starving and by increasing the tempera- 

 ture, but the latter was not effective with an optimum 

 supply of food. He found that more food than the 

 optimum produced effects similar to starving. Raising 

 the internal viscosity of the water by adding quince gum 

 produced no effect. He showed that though feeding in- 

 fluenced the differential growth, there was a cyclical 

 tendency for this to vary, viz., season-polymorphism. 

 However, the effects of prolonged abundant feeding were 

 inherited to some degree. 



One might interpret these results in different ways. 

 It is known that the temperature coefficients for various 

 chemical reactions are slightly different. Possibly the 

 mean of the temperature coefficients for the processes 

 in the development of the reproductive organs is higher 

 than the same for the body wall, and at a higher tem- 

 perature the germ cells would develop faster. However, 

 under adverse conditions the "affinity" of the repro- 

 ductive organs for nutriment is greater than that of the 

 rest of the body, so with deficient food the body wall is 

 retarded more than the germ cells in development. The 

 higher temperature may he considered an adverse condi- 

 tion since the mortality is greater. In this way starv- 

 ing has the same effect as a higher temperature. 



Langerhans 7 found that accumulation of excretions 

 caused shortening of the spine in daphnids. I do not 

 know what relation this bears to the above results. 



•"Ueber naturliche und kunstliche Varietatenbildung b<5i Daphniden," 

 Verb. Deutsch. Zool. Gesell.. l'M.s. ... L':lt; :u,.l " WVii.-rr experimentelle 



Artunterschiede bei Daplmiden," ibid., 1909, p. 110. 



'"Ueber experimented rntersiu-hungeii zu Fragen der Fortpflanzung, 

 Variation und Vererbung bei Daphniden," Verb. Deutsch. Zool. Gesell, 

 1909. p. 281. 



