1896. LYELL AND LAMARCKISM : A REJOINDER. 117 



life ; but that they are external insomuch as the agreement of the 

 " events " with the " law of frequency of error " is the effect of the 

 environment. 



When embryologists talk about the doctrine of evolution in em- 

 bryology as antagonistic to the doctrine of epigenesis ; when biologists 

 seek for the origin of species in laws of variation which are not the 

 outcome of selection ; when they talk about a " principle of organic 

 stability," which does not owe its origin to the same mechanism — it 

 seems to me that they fail to grasp the significance of Darwin's work, 

 and that they are wandering from the only path in which we can have 

 any well-grounded hope for progress ; the path which takes its depar- 

 ture in that conception of specific types which leads us to seek for the 

 origin of the " events " that exhibit the type in the structure of living 

 organisms, and to seek in the order of nature external to the organism 

 for the origin of that " law of error " which picks out a type from 

 among these events. 



The specific types of the zoologist and the botanist have peculiar 

 interest since they persist from generation to generation, according to 

 what is known as the law of specific stability ; while they also undergo 

 slow changes according to the principle of the mutability of species. 

 In popular language specific stability may be said to be due to 

 inheritance, and specific mutability to variation ; but in this con- 

 nection these words have only a loose meaning, and it has long seemed 

 clear to me that much of the current misconception of Darwin is due 

 to the fact that, in his desire to make clear the analogy between 

 natural and artificial selection, he borrowed these words from the 

 breeders without due deliberation. 



In so far as they give the impression that the stability of species 

 and the mutability of species are antagonistic to each other, that they 

 are due to two distinct and opposing influences, or that the individual 

 which is preserved is a " variation " in any sense which is not equally 

 applicable to the one which is exterminated, these words are 

 unfortunate ; for, notwithstanding Darwin's words, his context shows 

 clearly that he looks at both the stability and the mutability of species 

 as due to the same influence — the extermination by natural selection 

 of certain individuals, and the preservation of others and their 

 progeny. 



While a recent writer in Natural Scienxe (Nov., 1895) holds 

 that sexual reproduction is the cause of types, all students of the 

 subject are perfectly familiar with the fact that data drawn from any 

 source, living or dead, may conform to a type, and the excellence of 

 natural selection is not that it explains the existence of types, but 

 that it explains a distinctive peculiarity of the particular sort of types 

 which concern the zoologist and the botanist. These types not only 

 persist from generation to generation, but they also exhibit fitness. 

 It is this fitness, and not mere conformity to the statistical " law of 

 error," which calls for explanation, and gives to biology the rank of an 



