AGEING OF THE EGG AND DEVELOPMENT 



151 



h. At daily Intervals with the 20°C. female^ and every second day with the 10°C. 

 female, strip and fertilize about 100 egga from each frog into fresh standard 

 sperm suspension. Determine the number of egga fertilized, segregate, and care 

 for these egga as under "3" on preceding page. (It can be expected that the 

 uterine eggs at 20°C. may be fertilizable for about 5 to 7 days, while those 

 uterine eggs at 10°C. may be fertilized for 10 to 1*4- days. 



OBSEHVATIONS AITO DATA: 



There are three seta of data which are to be collected from these observations: 



1. The percentage cleavage at the different ages and temperatures* 



2. The percentage of cleaving eggs which gastrulate, neurulate, and hatch. 



3. The variety of abnormalities that are produced, correlated with the age of the 

 egg- 



The data should be complete and arranged in tabular form, but the final results 

 should be Indicated in the form of two graphs, one for the 20°C. eggs and another for the 

 10°C. eggs. Photographs, drawings, and cytological sections are very instructive. 



TEMPERATURE 



DAYS 



(Indicate data in percentages of total eggs for cleavages; but 

 In percentage of cleaving eggs for gastrulae and neurulae.) 



■eP- 



100 -, 

 75- 

 50 

 25H 



3^56 

 DAYS - AT 10°C. 



■rf!- 



100 -, 

 75- 

 50- 

 25- 



1+ 6 8 10 12 

 DAYS - AT 200c . 



11+ 



CLEAVAGE PERCENTAGE OF AGED EGGS 



