124 H - H - NEWMAN. 



emphasize the point that, though development ceases, certain 

 phases of vital activity continue almost unabated. 



In presenting the experimental results it seems advisable to 

 give in some detail the results of the first complete experiment, 

 which afterwards proved to be typical, and to follow this with a 

 relatively condensed account of several nearly identical experi- 

 ments that serve to corroborate the findings of the more in- 

 tensively studied first experiment. 



EXPERIMENT i. 



A fine batch of eggs, fertilized at 2.15 P.M., April 6, 1923, was 

 divided into four equal lots. After 17 hours, when the embryos 

 were still unhatched blastulae, but were rolling about within the 

 vitelline membrane, three lots were put on ice and one lot kept 

 under normal conditions as a control. One lot (i,A) was kept on 

 ice for one hour, a second lot (i, B] was iced for two hours, and a 

 third lot (i, C) was iced for three hours. After exposure to low 

 temperatures the experimental lots were placed beside the control 

 lot in a room with temperature of about 15 C. and allowed to 

 develop without disturbance for five days, at which time the first 

 definite signs of asymmetry may be observed. On the fifth day 

 both the control and the experimental lots were carefully looked 

 over with reference to the percentage of larvae showing reversal of 

 asymmetry. It was obvious under casual observation that there 

 were many more reversed larvae in the experimental lots than in 

 the control, but the exact difference could be determined only by 

 means of a census of a representative number of individuals from 

 each lot. 



The plan adopted was that of random sampling. A few larvae 

 at a time were picked up in a pipette and transferred to a Syracuse 

 watch glass and all examined to determine the position of the 

 posterior ccelom, a rather conspicuous object at this time. When 

 the count reached 100 the census was considered complete. This 

 might be considered too small a number to give significant data, 

 but when this is repeated a great many times it gains statistical 

 value. 



