E. E. Nelson and C. W. Greene 53 



the ovary, and not to the accumulation of extra-ovular fat. The 

 weight of the ovary is a fair criterion of the age of the ovary. 

 Because of the inability to differentiate between the source of 

 the various lipoid fractions, it would seem that a more accurate 

 picture of the metabolic changes might be gained by calculating 

 the data on a fat-free basis. This has been done in Table III. 



Proteins. 



There is a rather close approximation in the values for the 

 proteins, if Sample Cll and the single sample of Lepidosteus 

 osseus, 42a, be disregarded. Cll is a very much younger fish, 

 if one may judge by the weight of the ovaries and the diameter 

 of the ova. Greene (1918) showed for the salmon that the pro- 

 tein content of the ovary was remarkably constant throughout 

 the period of late development. Sample Cll is an interesting 

 case of an ovary which has not yet reached the average protein 

 content for the species. Its water content is the highest of all 

 the specimens examined. Sample 42a is obviously a much more 

 mature specimen. It has the highest protein, 28.4 per cent, 

 and the lowest water, 43.9 per cent, content of all the ovaries 

 studied. This might be explained on the grounds of the difference 

 in species. But Hatai (1917) has shown that in the white rat 

 there is an increase in protein and. a decrease in water content of 

 the whole body throughout the whole growth period. These 

 facts, especially when taken in conjunction with the variations 

 in the extractive fractions, argue for a more active stage of me- 

 tabolism in the early growth period of the gar ovaries. 



The average values for protein are in close agreement with 

 those found by Greene (1918) for the salmon. They also agree 

 closely with unpublished data for the ovaries of the carp. 



Organic Extractives. 



The organic extractives present in the tissue waters of all ani- 

 mal organs are an indirect measure of the metabolic processes 

 in the individual tissue. Hatai (1917) has shown that the tis- 

 sues of the growing white rat contain a greater proportion of 

 extractives than those of the adult. During the migration of the 

 king salmon Greene (1918) showed that the organic extractives 



