1892.] The Difficulties in the Heredity Theory. 555 
this, to my mind, is one of the strongest arguments against 
the possibilities of the rise of adaptive organs by the selection 
of chance favorable variations in the germ-plasm. 
Application to Human Evolution.—Principles underlying 
these illustrations may now be applied to some of the facts in 
human evolution brought out in the first lecture. They show 
that if functional tendencies are transmitted we can compre- 
hend the distinct evolution history of each organ; the rise 
and fall of two organs side by side; the definite and purposive 
character of some anomalies; the increase of variability in the 
regions of most rapid evolution; the correlation of develop- 
ment, balance and degeneration in the separate organs of the 
shoulder, hand and foot. 
Yet even granting this theory, there still remain difficulties. 
The relation of use and disuse to some of the contemporary 
changes in the human backbone is rather obscure. I would 
hesitate to pronounce an opinion as to whether our present 
habits of life are tending to shorten the lumbars, increase the 
spinal curvatures, and shift the pelvis, without making an 
exhaustive study of human motion. Among the influences 
which Dr. Lane has suggested’ as operative here are the wear- 
ing of heeled shoes and the increase of the cranium. He 
considers the additional or 6th lumbar vertebra as a new 
element rather than as a reversion, and works out in some 
detail the mechanical effects of the presence of the foetus upon 
female respiration (i.e, in the sternal region) and upon the 
pelvis. Now, if it be true that the female pelvis is relatively 
larger in the higher races than in the lower, I do not think that 
Dr. Lane can sustain his point, because in the lower races the 
foetus is carried for an equally long period, during a much more 
active life, and in a more continuously erect position. There- 
fore, if these mechanical principles were operating, the pelvis 
in the modern lower races should be larger than in the 
higher. On the other hand, the form of the female pelvis in 
the higher races is one of the best established selecting or 
eliminating factors, a large pelvis favoring frequent births 
- Journal of Anatomy and Physiology, 1888, p. 219. 
