892 



GENERAL METABOLISM 



[pT. m 



foundation in fact." Now the initial weight of wet yolk in a newly 

 fertilised trout's egg is approximately loo mgm., and, as 41 mgm. 

 of dry yolk is present, an amount of fish can be built up with these 

 materials corresponding to 256 mgm., for the water-content of the 



20 



70 



80 



90 



30 40 50 60 



Days after Fertilisation 



Fig. 234. 



final product may be taken at 84 per cent. Thus there is enough dry 

 material in the fertilised egg to produce an amount of fish two and 

 a half times its own weight. But, on the other hand, there are only 

 59 mgm. of water present in the original yolk, and this will be 

 sufficient for only 70 mgm. wet weight of fish. And the observed 

 weight of the fish at the end of the yolk conversion phase of develop- 

 ment is actually about 150 mgm. The explanation of all this is, of 

 course, that some of the initial dry material is lost during develop- 



