892 



iiCIENCK 



[N. S. Vol. XI. No. 284. 



the germs which are about to be budded off 

 from them will be so affected as to produce 

 exactly the same character — in this case 

 enlarged muscle, etc. — without the applica- 

 tion of the same stimulus, viz, exercise ? 

 Thus, while I freely admit that every altera- 

 tion of an organ in response to external 

 agents will react through the whole organi- 

 zation, affecting each organ in functional 

 correlation with the affected organ in a 

 way which will depend upon the function 

 of the correlated organ, and possibly other 

 organs not in functional correlation in an 

 indefinite way and to a slight extent, yet I 

 maintain that it is very hard to believe that 

 it will have such a sharp and precise effect 

 upon every spermatozoon and ovum subse- 

 quently produced that not merely will these 

 products be altered generally in all their 

 properties, but that one particular part of 

 them — and that part of them always the 

 same — will be so altered that the organisms 

 which develop from them will be able to 

 present the same modification on the appli- 

 cation of a different stimulus. It is incon- 

 ceivable ; unless, indeed, we suppose that 

 the very molecules of the incipient organs 

 in the germ are more closely correlated 

 with corresponding parts of the parent 

 body than are the homologous parts of the 

 parent body with one another. 



jSTow, to prove the existence of such a re- 

 markable and intimate correlation would 

 surely require the very strongest and most 

 conclusive evidence. Is there any such 

 strong evidence? I think I may fairly an- 

 swer this question in the negative. The 

 evidence which has been brought forward 

 in favor of the so-called inheritance of ac- 

 quired characters is far from conclusive. 

 That such evidence* exists I do not deny, 

 but it is all, or almost all, capable of receiv- 

 ing other interpretations. 



* For a good statement and discussion of the evi- 

 dence in favor of this view, see Romanes' Darwin 

 and after Darwin, Vol. II. chaps., 3 and 3. 



EFFECT OF CHANGED CONDITIONS UPON THE 

 REPRODUCTIVE ORGANS. 



On the other hand, all the certain evi- 

 dence we have concerning what happens 

 when the reproductive organs are affected, 

 either directly or by correlation, by a 

 change of conditions — and, as we have 

 seen above, they must be affected if there 

 is to be any change in the offspring — tends 

 to show that there is not any relation be- 

 tween the effect produced on the parent and 

 that appearing in the offspring. 



The only means of judging whether the 

 reproductive organs are affected by external 

 conditions is by observing any change 

 which may occur in their function. Now, 

 only two such phj'siological effects of a 

 change of conditions are certainly known ; 

 these are (1 ) the production of sterility or of 

 partial sterility ; (2) the production of an 

 increased but indefinite variability in the 

 offspring. AVith regard to the first of these 

 effects : One of the most common, or at any 

 rate one of the most noticeable alterations 

 in an organism, effected by change in the 

 external conditions, is an alteration of the 

 reproductive system, an alteration of such 

 a kind that organisms which had previ- 

 ously freely interbred with one another are 

 no longer able to do so. One of the most 

 common results of removing organisms 

 from their natural surroundings is to induce 

 sterility or partial sterility. There is no 

 reason to doubt that this sterility or ten- 

 dency to sterility is, broadly speaking, due 

 to an affection of the reproductive system. 

 In the case of the higher animals, it may 

 in some cases be due to an action upon the 

 instincts, but in the lower animals and in 

 plants we can hardlj' doubt that it is due 

 to a direct action upon the reproductive 

 organs. Indeed in plants these organs are 

 often visibljf affected. Among animals, 

 however, there does not appear to be any 

 satisfactory evidence on the point, and it is 

 not known what organs are affected, whether 



