6oz THE POPULAR SCIENCE MONTHLY. 



erations, is undeniable. Chinese are recognizable as Chinese in what- 

 ever part of the globe we see them ; every one assumes a black an- 

 cestry for any negro he meets ; and no one doubts that the less- 

 marked racial varieties have great degrees of persistence. On the 

 other hand, it is unquestionable that the likenesses which the mem- 

 bers of one human stock preserve, generation after generation, where 

 the conditions of life remain constant, give place to unlikenesses that 

 slowly increase in the course of centuries and thousands of years, if 

 the members of that stock, spreading into different habitats, fall under 

 different sets of conditions. If we assume the original unity of the 

 human race, we have no alternative but to admit such divergences 

 consequent on such causes ; and, even if we do not assume this origi- 

 nal unity, we have still, among the races classed by the community of 

 their languages as Aryan, abundant proofs that the subjection to dif- 

 ferent modes of life produces, in course of ages, permanent bodily and 

 mental differences : the Hindoo and the Englishman, the Greek and 

 the Dutchman, have acquired undeniable contrasts of nature, physical 

 and psychical, which can be ascribed to nothing but the continuous 

 effects of circumstances, material, moral, social, on the activities, and 

 therefore on the constitution. So that, as above said, one might have 

 expected that biological training would scarcely be needed to impress 

 men with these cardinal truths, all-important as elements in sociologi- 

 cal conclusions. 



As it is, however, we see that a deliberate study of Biology cannot 

 be dispensed with. It is requisite that these scattered evidences, which 

 but few citizens put together and think about, should be set before 

 them in an orderly way ; and that they should recognize in them the 

 universal truths which living things at large exhibit. There requires 

 a multiplicity of illustrations, many in their kinds, often repeated and 

 dwelt upon. Only thus can there be produced an adequately-strong 

 conviction that all organic beings are modifiable, that modifications are 

 inheritable, and that therefore the remote issues of any new influence 

 brought to bear on the members of a community must be serious. 



To give a more definite and effective shape to this general infer- 

 ence, let me here comment on certain courses pursued by philanthro- 

 pists and legislators, eager for immediate good results, but pursued 

 without regard of these biological truths which, if borne in mind, 

 would make them hesitate, if not desist. 



Every species of creature goes on multiplying till it reaches the 

 limit at which its mortality from all causes balances its fertility. Di- 

 minish its mortality, by removing or mitigating any one of these 

 causes, and inevitably its numbers increase until mortality and fertility 

 are again in equilibrium. However many injurious influences are 

 taken away, the same thing holds, for the reason that the remaining 

 injurious influences grow more intense. Either the pressure on the 



