One reason why the facts of delayedness and transitoriness in instincts have been so generally accepted without being thoroughly tested has been the belief in the recapitulation or repeating by the individual of racial development.  So long as this was accepted as explaining the development of inborn tendencies and their order of appearance, transitoriness and delayedness must necessarily be postulated.  This theory is being seriously questioned by psychologists of note, and even its strongest advocate, President Hall, finds many questions concerning it which cannot be answered.

The chief reasons for its acceptance were first, on logical grounds as an outgrowth of the doctrine of evolution, and second, because of an analogy with the growth of the physical body which was pushed to an extreme.  On the physiological side, although there is some likeness between the human embryo and that of the lower animals, still the stages passed through by the two are not the same, being alike only in rough outline, and only in the case of a few of the bodily organs is the series of changes similar.  In the case of the physical structure which should be recapitulated most closely, if behavior is to follow the same law,—­namely, in that of the brain and nervous system,—­there is least evidence of recapitulation.  The brain of man does not follow in its development at all the same course taken in the development of brains in the lower animals.  And, moreover, it is perfectly possible to explain any similarity or parallelism which does exist between the development of man’s embryo and that of lower animals by postulating a general order of development followed by nature as the easiest or most economical, traces of which must then be found in all animal life.  When it comes to the actual test of the theory, that of finding actual cases of recapitulation in behavior, it fails.  No one has been able to point out just when a child passes through any stage of racial development, and any attempt to do so has resulted in confusion.  There is no clear-cut marking off into stages, but, instead, overlapping and coexistence of tendencies characterize the development of the child.  The infant of a few days old may show the swimming movements, but at the same time he can support his own weight by clinging to a horizontal stick.  Which stage is he recapitulating, that of the fishes or the monkeys?  The nine-year-old boy loves to swim, climb trees, and hunt like a savage all at the same period, and, what is more, some of these same tendencies characterize the college man.  The late maturing of the sex instinct, so old and strong in the race, and the early appearing of the tendencies towards vocalization and grasping, both of late date in the race, are facts that are hard to explain on the basis of the theory of recapitulation.