126 



Investigations on the Life-History 



the ovaries in a similar manner ; and lastly, consider the inferences that 

 may be drawn from the changes observed. 



/. Percentage of Proteid in Muscle. Two samples of muscle from each 

 fish were examined, one from the under part of the fish (thin), the other 

 from the dorsal part (thick). It will be observed in the tables that the 

 "thick" muscle is, at all seasons, and in both estuary and upper- water fish, 

 richer in nitrogen than the " thin " muscle. This difference in the amount 

 of nitrogen, and consequently in the amount of proteid, emphasises the 

 importance of analysing both portions of the musculature as already 

 noted (p. 80). The smaller percentage of proteid in the thin muscle is 

 probably dependent on the larger percentage of fat there (vide p. 83), 

 the fat of course increasing the weight reduces the percentage of other 

 constituents present. 



The amount of proteid of the muscle in estuary fish is fairly constant 

 throughout the season. It is slightly higher in July and August than 

 in May and June, and slightly lower in October and November than in 

 the earlier months. The fish which show the greatest divergence from 

 the average are Nos. 72 and 79. These fish were caught in the estuary 

 late in the year (winter salmon), had undeveloped ovaries, and would not 

 spawn till the following year. Their muscles were laden with fat, and 

 consequently the percentage of proteid was lower than the average. 



The muscles of the upper- water fish show more change. Those of the 

 fish caught in October and November have a much smaller amount of 

 proteid than the earlier fish. This percentage diminution is not due to 

 increase of fat, as in 72 and 79, the amount of fat being diminished, but 

 is due to an increase in the water of the muscle (page 84). The upper- 

 water fish from May to August have a fairly constant percentage of 

 proteid, and that percentage is nearly the same as in estuary fish 

 throughout the series. 



TABLE V. 



Showing the percentage of nitrogen in the muscle of the different 

 groups of fish : 



//. Total Muscle Proteid of the Fish. In considering this point two 

 comparisons suggest themselves. Firstly, comparing the muscles of the 

 fish of the later periods of the year with the earlier ones; and, 

 secondly, comparing the muscles of the upper- water fish with those of 

 the estuary fish. 



The estuary fish, as is seen in Table III, have a nearly constant 

 amount of muscle nitrogen throughout the season, the aveiage for the 



