GROWTH AND DEVELOPMENT 



77 



ing. while quite similar for the three species of game is, however, much smaller than in some 

 domesticated hirds. such as poultry. This means that grouse, after hatching, can survive only 

 a relatively short time without food. 



The chemical analysis of newly hatched grouse showed some annual changes during the 

 five-year period. However, the occurrence of a few highly variable values frequently inter- 

 fered with the analysis of these chemicals. For example, in most of the clutches the weight 

 of a chick without the yolk was the lowest in the year 1937 (figure 6). but the average to- 

 tal weight was nearly the same as in the other years. 



14 





1936 



J L 





I 



1937 



12 3 4 



J L 



J_ 



_L 



4: 



• 6 





I 



t 



• • • INDIVIDUAL WEIGHTS 

 o AVERAGE PER CLUTCH 



1938 



j_ 



_L 



_L 



o I 



1940 



J L 



I 2 3 



1234 1234567 123 



INDIVIDUAL CLUTCHES 



FIGURE 6. ANNUAL CHANGES IN THE WEIGHT. WITHOUT YOLK SAC, OF NEWLY HATCHED 

 GROUSE COLLECTED FROM THE ITHACA, NEW YORK, REGION — 1936-1910 



Besides these variations, it is also possible that the selected measurements were not signifi- 

 cant. More delicate measurements of physical and chemical phenomena of embryonic devel- 

 opment may. however, disclose greater annual differences in embryonic metabolic activity. 



It is a question whether deviation in such activity could have been responsible for the 

 lower viabilit> atui early death of certain embryos, and thereby be one of the causes of 

 low grouse abundance. 



GROWTH AND DEVELOPMENT* 



The phenomenon of changing the protective coat coincident with growth of animals is ac- 

 complished in many interesting ways. Fishes, for instance, retain the covering in which they 

 are born but the scales increase in size and afford complete protection throughout life as 



» By Earl R. Holm. 



