pa 
1871.] 25 1 (Cope. 
B. CHANGE rn AMOUNT OF GROWTH FORCE. 
1. Absolute increase of Growth Force.—As every type has had its period 
of greatest development in numbers, size, and complication of structure, 
the present law indicates as an explanation, a culmination of the pro- 
cess of conversion of growth force from its energetic to its potential state 
in tissue. The cause is primarily the increased exercise of effort and 
use, which while effecting a conversion, increases the capacity of the or- 
gans by which further conversion is effected. 
2. Local increase of Growth Force.—Examples of a local increase of this 
kind are probably to be seen in convoluted organs ; as the convolutions 
of the brain in higher Mammalia ; the convolutions of the enamel of the 
Labyrinthodont Batrachia; the same phenomenon in the cotyledons or 
plumule of some seeds. In these cases the superficial area of the parts 
is excessively developed, and the inclosing organs not being proportion- 
ately enlarged, a convolution necessary follows. In the first case, the 
skull; in the second, the alveolus ; in the third case, the seed-envelope, 
restrain the expanse of the contained part, which would otherwise follow 
increase of growth force. 
3. Absolute loss of Growth Force.—This will follow defective nutrition, 
produced by inability of the animal to obtain heat and food requisite 
to that end. This is supposed to be due (according to the view hereafter 
proposed) primarily to deficiency of intelligence, in failing to adapt habits 
to changed physical circumstances, and secondarily to the unfavorable 
influence of such changed circumstances. The extinction of highly 
specialized types, which has closed so many lines of animal types, will be 
accounted for by their less degree of plasticity and want of capacity for 
change under such changed circumstances. Such changes consist of mo- 
dified topography and temperature, with irruptions of many new forms 
of life by migration. The less developed, forms would be most likely to 
experience modification of structure under a new order of things, and 
paleontology teaches that the predecessors of the characteristic types of 
one period were of the less specialized forms of that which went before. 
Thus is explained the fact that, in following out the line of succession 
of animal forms we have constantly to retrace our steps from specialized 
extremes, (as osseous fishes, tailless Batrachia, song birds, etc.), to more 
generalized or simple forms, in order to advance beyond. 
4, The complementary diminution of growth nutrition follows the excess 
of the same in a new locality or organ, of necessity, if the whole amount 
of which an animal is capable, be, as I believe, fixed. In this way are ex- 
plained the cases of retardation of character seen in most higher types. 
The discovery of truly complementary parts is a matter of nice observa- 
tion and experiment. Perhaps the following cases may be correctly ex- 
plained, 
A complementary loss of growth force may be seen in absence of 
superior incisor teeth and digits in ruminating Mammalia, where exces- 
sive force is evidently expended in the development of horns, and com- 
