3i8 SCIENCE PROGRESS i 



ment a little before their innate powers of growth are exhausted, and are 

 therefore able to proceed to a yet higher level of efficiency with an accompany- 

 ing additional development of structure. And the result of this addition is 

 to make them in their turn the fittest of their generation, and the progenitors 

 of the next. Let us note in passing that the nature of this addition is largely 

 determined by the pressure of the environment on the still plastic organism 

 — it is pre-eminently an adaptation, or what is called an acquired character. 

 In addition by precocity the organism is enabled to put to an earlier test, and 

 so profit by, any superiority which it may owe to a favourable spontaneous 

 variation of the germ from which it grew. It is to such variations that we 

 must still look for improvement in such developments as hair, feathers, and 

 teeth, so far at all events as they are incapable of stimulation by exercise 

 or the incidence of surrounding forces. But how much as a rule must an 

 adaptation made in actual response to those forces exceed in value ajiy 

 improvement that can be expected to appear spontaneously 1 



These are the chief advantages of precocity, and they seem great enough 

 to warrant the assertion that in a great majority of cases only those who 

 attained the parental level of efficiency while still relatively young and 

 adaptable — only the precocious — would have any chance of reaching the 

 final and crowning adaptation of their own generation, and consequently a 

 yet higher level of efficiency in the struggle for life. 



Now let us suppose that in any of the higher animals the fittest of genera- 

 tion B, having by this road of precocity passed their parents, generation A, 

 in efficiency, are then in their turn surpassed by the fittest of their ofispring, 

 generation C, then the crowning structural modification of B, which made 

 its possessors the best of their generation, has become in C the penultimate 

 phase of growth, and the crowning adaptation of A the ante-penultimate 

 phase. These two phases are still attained late in the course of development, 

 but no longer at its very end. It is still the environment that evokes and 

 moulds them, but the response is quicker, and they are evoked in a shorter time. 

 But now, if we suppose this process of acceleration to be repeated indefinitely 

 generation after generation, what must be the result in generation N, taking 

 that letter as in Algebra, to signify a number indefinitely large ? Clearly 

 the crowning adaptation of the fit of generation A , by which they established 

 their claim to fitness and to be the progenitors of the future race — an adapta- 

 tion reached by them only after long and arduous exercise in a hostile environ- 

 ment, probably among a host of rivals, and possibly by strenuous exertion 

 of a more or less conscious will-power — would be attained by generation N, 

 after the lapse of perhaps hundreds of thousands of years, in a very short 

 time in the normal course of what is called natural growth, without exercise 

 or the exertion of any will-power at all, and as nearly as can be without 

 reference to the forces of the environment, as the bird is now fledged, and 

 develops its powerful wing-muscles before ever it leaves the nest. And this, 

 it seems to me, is what has happened in fact. In other words, by the accumu- 

 lation of small, often perhaps imperceptible, advances made by individual 

 generations, coupled with constant precocity, what we call acquired characters, 

 and Spencer more accurately called " functionally produced modifications," 

 have been gradually converted in process of time into congenital characters, 

 the common birthright of every member of generations long subsequent to 

 their origination, reached by them early in life, perhaps even (it is a question 

 only of time for the accumulation of sufficient precocity) long before hatching 

 or birth. 



For reasons obvious enough, and good as far as they go, it is customary 

 to draw a sharp line of distinction between the two kinds of character, germinal 

 and acquired, and this may make it difficult to realise that they are not 

 essentially different. But such is the fact. Acquired characters are evoked 

 out of the growth of the germ by converse with the environment, and no 



