266 ESSENTIALS OF BIOLOGY 



We have seen that mutations appear ; can be loosely incorporated 

 in the developmental organization ; can be reassorted in each 

 hybridization that occurs from sexual mating so that we can 

 have combinations of characters, or transformism. But all this 

 occurs under human control and we must extend the results to 

 wild nature before we can attempt to explain evolution. Here 

 again the appeal to natural facts — to the populations living in the 

 wild — fails. We know that races of organisms have been domesti- 

 cated, reared, inbred, etc., so that transformism undoubtedly 

 occurs under artificial conditions, but this is not enough : we have 

 to show that there are analogous processes operative in wild nature 

 and this has not been demonstrated. So, with regard to Lamarck- 

 ian transformism, we have to show that acquirements made by, 

 or experienced by individual organisms can change the develop- 

 mental organization so that these acquirements become hereditary 

 changes. 



All that can be said is that the meagre evidence that we have 

 points to that conclusion. There is, of course, much experi- 

 mental " proof " that this is not the case — proof that hardly 

 apphes to our problem. Undoubtedly it has been most difficult, 

 and perhaps impossible, to show that experimentally produced 

 mutilations become hereditary. For instances, the tails of many 

 generations of rats and terrier dogs have been amputated but 

 still the descendants of many generations of such mutilated 

 animals are quite normal and do not exhibit the mutilation. We 

 ought to be very much surprised if we did obtain such a trans- 

 mission of a mutilation, for we have only to reflect that all 

 organisms in wild nature are continually exposed to innumerable 

 risks and suffer from the results of accidents. We know that, 

 even before reproductive vigour has failed animals have " aged " 

 and have acquired disabilities — which nevertheless do not reappear 

 in their progeny. Nothing is more surprising, upon due reflec- 

 tion, than that experimental mutilations should have been practised 

 upon animals with the expectation that those changes would 

 reappear in the progeny. It is even more surprising that the 

 failure to obtain such results should have been held to be a 

 demonstration that Lamarckian transformism did not occur. 



It is different with regard to adaptations. It seems " reason- 

 able " to expect that slight, advantageous changes, made generation 

 after generation, would eventually affect the developmental 



