June 8, 1900.] 



SCIENCE. 



893 



it is the actual gametes, or the reproductive 

 glands, or some of the other organs con- 

 cerned.* 



The other result of changed conditions 

 which is certainly known is to induce an 

 increased amount of variability of the ge- 

 netic kind, though not immediately, often 

 indeed not until after the lapse of some 

 generations. On this point Darwin says : 

 ' ' Universal experience shows us that when 

 new flowers are first introduced into our 

 gardens they do not vary ; but ultimately 

 all, with the rarest exceptions, vary to a 

 greater or less extent" (' A^ariation,' 2, p. 

 249 ).t With regard to the variability thus 

 induced, it is to be noticed that it is not 

 confined to anj'^ particular organ, nor does 

 it show itself in any particular way. On the 

 contrary, the whole organization is affected, 

 and the variations are quite indefinite. 



To sum up the argument as it at present 

 stands : (1) a change in conditions cannot 

 affect the next generation unless the repro- 

 ductive organs ai'e affected ; (2) from a 

 consideration of the facts of the case, it is 

 almost inconceivable that the effect pro- 

 duced upon any organ of a given organism 

 by a change of conditions should so modify 

 the reproductive organs of that organism 

 as to lead to a corresponding modification 

 in the offspring without the latter being 

 exposed to the same conditions; (3) the 

 only effects, which are certainly known, of 

 changed conditions upon the reproductive 

 organs are (a) the production of sterility ; 

 (h) an increase in genetic variability. 



* The exact cause of this sterility in the higher 

 animals is a point which specially needs investigation. 



t The phenomenon of increased variability follow- 

 ing npon change of conditions has most often been 

 observed when the change has been from a state of 

 nature to a state of cultivation. Hence the conclu- 

 sion has been drawn that the kind of change involved 

 in domestication alone induces variation. But there 

 is no evidence in favor of this view. The evidence 

 shows that change of conditions in itself may induce 

 greater variability. 



As far then as our certain knowledge 

 goes, it would appear that a change of con- 

 ditions may have one or both of the follow- 

 ing effects : 



(1) A definite change, of the same char- 

 acter or nearly so, in all the individuals 

 acted upon . Such changes may be adaptive 

 or non-adaptive, but they are not perma- 

 nent, lasting only so long as the change of 

 conditions, or at most during the life of the 

 individual acted upon. They are not trans- 

 mitted in reproduction, and do not appear 

 in the offspring unless it is submitted to the 

 same conditions. These variations are the 

 direct result of the action of the environ- 

 ment upon the individual, with the excep- 

 tion of the reproductive organs. 



(2)_ Increase in the variations of the ge- 

 netic kind. These are seen not in the gen- 

 eration* first submitted to the changed con- 

 dition, but in the next or some subsequent 

 generations. The effect is produced through 

 the reproductive organs. These variations 

 are non-adaptive, and different in each in- 

 dividual. 



If the reproductive organs are affected 

 we get an increase in the variations of the 

 genetic kind. These, we have seen, are 

 usually of an indefinite character ; they are 

 different in every case, and their nature 

 cannot be predicted from experience. But 

 we still have to ask : Is this a universal 

 rule ? Does it never happen that a change 

 of conditions so affects the reproductive or- 

 gans as to produce a definite non-adaptive 

 change of the same character or nearly so 

 in all the descendants of the individual 

 acted upon? This is the most obscure 

 question connected with the study of vari- 

 ations. If such changes occur, they might 



* Xo doubt the individuals of the generation first 

 submitted to the changed conditions would be affected 

 as regards their reproductive organs, which would be 

 altered in structure, but this has not been made out, 

 though there are indications of such an effect in cer- 

 tain plants. 



