58 ORGANIC EVOLUTION — THE FACTORS 



unworthy of discussion. Rejecting this and other 

 similar theories, I think that those who maintain the 

 transmissibility of acquired variations are practically 

 reduced to the choice of one of the -three following 

 hypotheses. The first of these supposes that an 

 acquired variation produces, through the blood, such 

 changes in the nutrition of the germ cell as bring about 

 after fertilization a similar variation in the organism 

 of which its remote cell-descendants form the com- 

 ponent parts. To take the same example as before, 

 it is supposed by this theory that the blacksmith, by 

 exercising the muscles of his arm, produces such a 

 change in tl^e nutritive fluids which bathe his germ 

 cells as causes them, after conjugation with germ cells 

 from another individual, to proliferate in such a manner 

 as to produce new organisms with muscles similarly 

 enlarged. To my mind this is as wild a theory, as 

 that, which I have already dismissed. Even were it 

 possible, and I think i it is impossible, that such 

 transient changes as are produced in the nutritive 

 fluids by exercising the arm muscles could so perma-' 

 nently and profoundly affect the constitution of the 

 germ cell as to cause it to develop, after long separation, 

 from the parent organism, into an individual structurally 

 different from the individual which would otherwise 

 have resulted, even, I- say, were this possible, how is 

 it possible that these nutritive changes can cause in 

 the germ cell such ;particvjlar structural alterations as 

 result, after its proliferation, in an individual who has 

 a variation similar to the particular variation in the 

 parent organism, a variation which resulted from' 

 exercising the arm muscles ? To put it in fewer words : 

 how can the change which any acquired variation 

 produces in the nutritive fluids that bathe the germ 

 cell affect that cell in such a manner as to cause it, 

 after fertilization and separation from the parent 



