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TEMPERATURE AND EMBRYONIC DEVELOPMENT 



THE EFFECT ON DEVELOPMENT OF 

 TEMPORARY DRASTIC TEMPERATURE CHANGE 



Three temperatures are to be used for these observations, but two of them are to be be- 

 yond the normal range of viability. Prepare an incubator which is controlled at about 

 33° to 35°C. and a refrigerator at or near 0°C. Place four finger bowls, each with 50 

 cc. of the appropriate medium, at each of these temperatures. If possible, adjust the 

 control temperature at 18°C. comparable to the Shumway series. 



1. Pre-cleavage exposure to radical temperature : Inseminate healthy eggs of Rana 

 pipiens and, after flooding and allowing them to swell (about 1 hour) cut them into 

 clusters (5 to 10 each), and place 25 in each of the 10 finger bowls (4 at C. , 2 at 

 18 C. , and 4 at 33 C. ). Record the exact time on each bowl with China marking pen- 

 cil. At exactly 1, 2, 6, and 24 hours thereafter remove one finger bowl from each of 

 the two radical temperatures, and place it in the environment of the 18°C. control 

 eggs (providing it is large enough and adequately controlled to take care of the drastic 

 temperature invasion). Note the condition of the eggs in each bowl at the time of re- 

 moval from the drastic temperatures, and the condition (stage) of the controls. 

 Follow the subsequent development of all treated and control eggs to determine the 

 effect of these radical temperatures at this early stage of development. 



PRE-CLEAVAGE RADICAL TEMPERATURE TREATMENT 



* 50« of eggs. 



