case of land vertebrates, which produce much fewer eggs but fir- 
nish these with greater nutriment and give them special care, 
there is similar exhaustion, as also in the case of mammals, ia 
which a considerable development of the young takes plat 
within the body of the parent. Thus asa rule growth ceases 
shortly after the period of sexual maturity is reached. The leat 
exhaustive phase of this process is that displayed by the males of 
mammals, which lose but little vital material and waste little 
vital strength. They consequently exceed the female in size, yet 
not inordinately. The conformity in hereditary conditions, an 
in size of the initial life stage, act to prevent any undue excess in 
growth of males over females. 
The conflict between reproduction and individual energy, how- 
ever, is but one of the influences affecting the sizes of animal. — 
There are conditions which affect the members of each separatt | 
tribe to which we must next advert. Whether two animals shal | 
attain the same size does not depend entirely on whether they are | 
able to obtain the same quantity of food. This is but one elè- ? 
ment in the problem. Another equally important element isthe | 
amount of exertion, physical or mental, necessary to obtain A 
food. The food is not applied within the body to the single pe 
pose of growth. Itis partly consumed in the production of = 
mal heat, partly in recovering from muscular waste, esi 
similar nerve recovery, and partly in reproductive activity, Ls 
only its excess goes to the formation of permanent new aie | 
As a rule it might be conjectured that cold-blooded animl ; 
would exceed the hot-blooded in size. They obtain their ™ 
from without, and use up no nutriment in this purpose k 
they are less active and efficient in the pursuit of food, and x 
more than lose the advantage which their nutrient su pa 
might give them. Muscular activity is very exhaustive 0t 1 
ment, and we find that the more active animals are us bine 
smaller. Thus throughout their whole range the Hee i 
exceed the Carnivora in size. And of each of these class be 
most active species are the smaller. The great Carer 
lions and tigers, are only occasionally active. The a 
‘sluggish in movement. The smaller Carnivora, as pee 
family, are incessantly active. It is the same with the af ot 
The elephant, rhinoceros and hippopotamus are | us pi a 
_ Moving creatures, The ox family is more active, and : 
irog Reena Growth, its Conditions and Variations. [November 
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