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O. 16 



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O. 13 



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DAYS 



Fig. 3. The Changes in the Nitrogen Content of Two Sets of Frog 

 Embryos, left on the Spawn after Hatcliing and Removed from it 



Note that there is no appreciable diflference. In fact, one set gained more 



when on the jelly, and the other gained less. Note also the large difference 



in the two sets of embryos. Black circles on spawn. Open circles, not on 



spawn. Black and open circle, near spawn. 



18 



