1100 Growth, its Conditions and Variations. [November l 
a full share of the naturally supplied food. This has been one 
of the most potent agencies in the history of animal develop- 
ment. The living tribes of nature sit down to a bountifully sup- 
plied table from which each eagerly seeks to gain a “lions 
share” of food. Of those that are adapted to a certain kind 
of food, on a certain part of the table, the best armed and 
situated will obtain the most, and increase in size over their less 
fortunate competitors. On another part of the table animals 
equally well armed are served with a more meager repast, and 
thus need greater activity to obtain equal or smaller quantities of 
food. They consequently decline in size below their better situ- 
ated relatives. The degree of competition, however, is reduced 
by the fact that many tribes are adapted to food of quite different 
kinds from that sought by others. Yet every class of foods 
eagerly sought for, so that there is everywhere a sharp compe 
tion, and the animal so organized and situated as to obtain the 
most with the least exertion of body or mind, is sure to outgrow 
all rivals of equal advantages and initial powers of organization 
It may be here remarked also that at this great feast of nature 
the food often resists capture, and is not to be taken without sp 
cial exertion. Some offers no resistance, some is enclosed in 
hard or spiny armor, some has active powers of mones 
needs to be pursued. Thus the competition is great m a 
and in variety, and the sizes attained by the different gues “g 
pend greatly on the quantity of food they succeed in ey 
in fixed periods, and the waste of tissue necessary 1 
struggle. i a 
This competition, while highly influential in keeping epee 
animals each to its limit of size, was probably, in the geol of ati 
periods, the most efficient agent in controlling the saen fi 
mals, far more so than the direct struggle between eure ae 
their prey. A rapid review will show this. In tracing oe 
cession of animals in former ages one fact of impo a slow 
This is, that the members of ‘the animal kingdom only by a 
degrees advanced in the utility of their weapons of 3 const” 
defence, in their agility and in their mental ability. r period 
quence of this successive development the geolog! i aniol 
present us with some highly interesting conditions Successit 
life, which are of interest in the present connection. 
waves of life have passed over the earth, each swelling t08 = 
