LEONARD MUSCATINE 



261 



10 



FED EVERY SECOND DAY 



GREEN 



t ALBINO 



TIME IN DAYS 



Fig. 5. Same as Figure 4 but fed every second day. Arrow denotes time of 

 feeding. 



day, green liydra deviated only slightly from normal logarithmic 

 growth. But under the same conditions, albino hydra showed not 

 only a more pronounced deviation, but also required more time to 

 regain normal growth after feeding was resumed. More striking dif- 

 ferences appeared when these two groups were fed every third 

 day. Figure 6 illustrates the sharp decline in rate of budding by 

 both groups during the interval without food. But after feeding, 

 green hydra immediately resumed a normal maximum growth rate. 

 In contrast, growth of albinos lagged and did not return to normal. 

 The effect of complete elimination of food is shown in Figure 7. 

 Ten hydranths of each kind were removed from mass cultures and 

 starved in the light in 30 ml. of M solution in Petri dishes (4" 

 diam.). The culture medium was renewed once daily. Under these 

 conditions, green hydra continued to produce buds for 7-9 days and 



