No. 4.] 



THE DEVELOPMENT OF ANIMALS. 



181 



TABLE I. Table showing the time of regeneration at different temperatures of the posterior 



half of Plciiiaria torva. 



six months the eyes and brain were still incomplete. Three of 

 the others died before the six months were up ; two lived and 

 showed no signs of regeneration, though they were responsive 

 to stimuli all the time. These two were then put at room tem- 

 perature, and one regenerated fairly normally, while the other 

 showed no sign of regeneration, though it remained alive for 

 several days. 



The optimum temperature is 29.7 C., and the time of regen- 

 eration at this temperature 4.6 days, the fortieth part of the 

 time at 3 C. At 31.5 C. regeneration was slower, 8.5 days. 



The curve which follows (Fig. i) shows the law of rate of 

 increase. 



Between the minimum and the optimum the rate of decrease 

 in time (increase in rapidity] of development diminishes with 

 each degree rise in temperature. Let x equal the decrease in 

 time for each degree increase of temperature, then : 



From 



3 to 



9 C., x = 22.23 days. 



b. Subminimal and Supramaximal Temperatures. - - Very 

 little effect was observable in the case of the subminimal tem- 

 peratures. Some of the anterior halves showed a slight ten- 



