Cope.] 262 [Dee. 15, 
plication of stomach and digestive organs. The excess devoted to the latter 
region may account for the lack of teeth at its anterior orifice, the mouth ; 
otherwise, there appears to be no reason why the ruminating animals 
should not have the superior incisors as well developed as in the odd toed 
(Perissodactyl) Ungulates, many of which graze and browse. The loss 
to the osseous system in the subtraction of digits may be made up in the 
development of horns and horn-cores, the horn sheath being perhaps the 
complement of the lost hoofs. It is net proposed to assert that similar 
parts or organs are necessarily and in all groups complementary to each 
other. The horse has the bones of the feet still further reduced than the 
ox, and is nevertheless without horns. The expenditure of the comple- 
mentary growth force may be sought elsewhere in this animal. The lat- 
eral digits of the Hquidw are successively retarded in their growth, their 
reduction being marked in Hppotheriwm, the last of the three-toed horses ; 
it is accompanied by an almost coincident acceleration in the growth 
nutrition of the middle toe, which thus appears to be complementary to 
them. 
The superior incisors of the Artiodactyla disappear coincidentally with 
the appearance of horns, which always exist in the toothless division of 
the order, except in some very small antelopes (Cephalophus, etc.) where 
the whole amount of growth force is small. Possibly the superior inci- 
sors and horns are complementary here. The retardation in development 
of the teeth in the higher apes and men, as compared with the lower apes 
is coincident with the increase of number of brain conyolutions. That 
this is not necessarily coincident with reduction of teeth in other groups 
is plainly proven by the rodents“and Chiromys where the loss of many 
teeth is complementary to the great size of the incisors of the middle 
pair. But in man there is no complementary increase of other teeth, and 
the reduction is no doubt due to contraction of the jaws, which is com- 
plementary to increase in other parts of the cranium, in both apes and 
men. ; eka 
Iam confident that the origin and loss of many structures may be ac- 
counted for in this way, and the correlation of parts to each other be 
measured accurately. 
Objection. The first one which arises is that which the author of the 
Vestiges of Creation made against Lamarck’s theory of a similar kind, 7. ¢. 
that by assuming that effort, use and physical causes have originated modi- 
fications of structure, we give the adaptive principle 100 much to 
do. I have made the same objection to the theory of natural selec- 
tion. It is true that an application to a purpose is involved in the pres- 
ent theory of the ‘*‘location of growth force;’’ but in point of fact, a large 
nuimber of non-adaptive characters are accounted for by it. These are 
the rudimental and transitional ones which mark the successive steps 
preliminary to the completion of an adaptive structure; second, those 
produced by deficiency of growth force in less favored regions of the body, 
and third and fourth, phenomena consequent on general deficiency and ex- 
cess of growth force, 
