SECT. 2] 



AND WEIGHT 



519 



These preliminaries concluded, one can examine the results of 

 Crozier for growth in general and embryonic growth in particular. 

 He found on examining the figures for the growth at different 

 temperatures of Drosophila melanogaster embryos (and larvae) (Loeb 

 & Northrop and Krafka) and of the pupae of Tenebrio molitor (Krogh) 

 that there were two temperature characteristics, 27,000 below 15° 

 and about 10,000 above 15°. This was evidence that whatever the 



00034 



COOdD 



00056 



Fig. 81. Temperature characteristics of early development in the frog. A, Krogh's data 

 (first cleavage) ; B, Lillie & Knowlton's data (from first cleavage to disappearance of 

 yolk-plug); C, Lillie & Knowlton's data (from other cleavages to disappearance of 

 yolk-plug) ; D, Krogh's data (later development) . 



limiting factor in growth was, it was not an oxidation process, a 

 conclusion that was strongly supported by the data of Loeb & 

 Wasteneys and Loeb & Chamberlain for the velocity of segmentation 

 (first cleavage) of echinoderm eggs. This worked out at 41,000 below 

 about 11°, 21,000 between 11° and 16°, and 12,400 above 16°. 

 Krogh's data, again, for the segmentation of frog's eggs, gave 

 22,600 below 13-5° and 10,200 above 13-5°. In no case, therefore, 

 was a typical oxidation temperature characteristic obtained for the 

 earliest stages of embryonic growth. 



