November 20, 1896.] 



SCIENCE. 



739 



will force it to start at a lower level, and 

 will prevent its going so far. If natural 

 selection take place at all, we may well be- 

 lieve that it would do so under such cir- 

 cumstances. * And it would work along 

 the lines laid down for it in adaptive modi- 

 fication. Modification would lead; varia- 

 tion follow in its wake. It is not surprising 

 that for long we believed that modification 

 was transmitted as hereditary variation. 

 Such an interpretation of the facts is the 

 simpler and more obvious. But simple and 

 obvious interpretations are not always cor- 

 rect. And if, on closer examination, in the 

 light of fuller knowledge, they are found to 

 present grave difficulties, a less simple and 

 less obvious interpretation may claim our 

 provisional acceptance. 



In his recent paper on G-erminal Selection 

 Prof. Weismann says:f " I am fain to re- 

 linquish myself to the hope that now, after 

 another explanation has been found, a rec- 

 onciliation and unification of the hostile 

 views is not so very distant, and that then 

 we can continue our work together on the 

 newly laid foundations." As one to whom 

 Prof. Weismann alludes as having ex- 

 pressed the opinion that the Lamarckian 

 principle must be admitted as a working 

 hypothesis, I am now ready to relinquish 

 myself also to the same hope. Germinal 

 Selection does not convince me, though I 

 regard it as a suggestive hypothesis; and 

 assuredly I am not convinced by the argu- 

 ment that because in certain cases, siich as 

 the changes in the chitinous parts of the 

 skeleton of insects and Crustacea, and in 

 the teeth of mammals, use and disuse can 

 have played no part, therefore in no other 

 cases has use-inheritance prevailed. Even 

 Homer sometimes nods, and Prof. Weis- 

 mann's logical acumen seems to have de- 



* Prof. Weismann's ' Germinal Selection ' if a vera 

 causa would be a cooperating factor and assist in pro- 

 ducing the requisite variations, 

 t Monist, loc dt, p. 290. 



serted him here. But it appears to me that 

 on the lines I have sketched out, it is open 

 to us to accept the facts adduced by the 

 transmissionists and at the same time in- 

 terpret them on selectionist principles. 



It may be well now briefly to summarize 

 the line of argument in a series of num- 

 bered pai'agraphs. 



1. In addition to what is congenitally 

 definite in structure or mode of response, 

 an organism inherits a certain amount of 

 innate modifiability or plasticity, 



2. Natural selection secures : 



(a) such congenital definiteness as is 

 advantageous. 



(&) such innate plasticity as is advan- 

 tageous. 



3. Both a and b are commonly present; 

 but uniformity of conditions tends to em- 

 phasize the former variable conditions of 

 life, the latter. 



4. The organism is subject to : 



(a) variation of germinal origin. 



(b) modification of environmental ori- 

 gin, affecting the soma or body tis- 

 sues. 



5. Transmissionists contend that somatic 

 modification in a given direction in one 

 generation is transmitted to the reproduc- 

 tive cells to constitute a source of germinal 

 variation in the same direction in the next 

 generation. 



6. It is here suggested that persistent 

 modification through many generations, 

 though not transmitted to the germ, never- 

 theless aflbrds the opportunity for the oc- 

 currence of germinal variation of like nature. 



7. Under constant conditions of life, 

 though variations in many directions are 

 occurring in the organisms which have 

 reached harmonious adjustment to these 

 conditions, yet natural selection eliminates 

 all those which are of such amount as to 

 be disadvantageous, and thus acts as a 

 check on all variations, repressing them to 

 within narrow limits. 



