March 28, 1902.J 



SCIENCE. 



489 



ural world is in the interrelations between 

 things, and not in unknown and unknow- 

 able things as they are in themselves; 

 does it not follow that scientific discov- 

 ery is the only way to learn the differ- 

 ences betAveen things, just as it is the only 

 way to learn the resemblances between 

 things? When we say two things are the 

 same, must we not also say what are the 

 relations with reference to which they are 

 the same? When we say they are differ- 

 ent, must we not also say what are the 

 relations with reference to which they are 

 different? Is there any way except scien- 

 tific discovery to find this out? 



15. The biological problem of species. 



Fifty years ago many naturalists 

 thought that all living things of a kind are 

 fundamentally and absolutely alike in cer- 

 tain specific characters, and that it is only 

 in characters that are not specific that they 

 differ; but more exact study has failed to 

 show us, in any living being, any charac- 

 teristic whatever which does not exhibit 

 diversity from others of its kind, as well 

 as resemblances; for the notion that cer- 

 tain characters are generic, while others 

 are differential, is an illustration of the 

 fallacy of the undistributed middle, as is 

 also the attempt to analyze living beings 

 into characters. 



After- the long controversy between 

 those who asserted the immutability of 

 species, and those who declared that spe- 

 cies are mutable, seemed to be happily 

 ended by the scientific demonstration that 

 species have a natural history, there arose 

 a new school of naturalists, who asserted 

 that species have no existence in nature 

 because no two living beings are identical 

 in any respect Avhatever. At the present 

 day, many naturalists are returning to a 

 modification of the old notion of species, 

 and are teaching that while the mutability 

 of species is due to changes in the interre- 

 lations between living beings and the 



world around them, stability is inherent in 

 the living beings, as they are in themselves 

 by birth. 



If the view which is here advanced be 

 correct, the specific stability of the indi- 

 viduals of a species is real, and as inde- 

 pendent of us as the stability of the sun 

 in the heavens, but when we say the indi- 

 viduals of a species are alike, we must also 

 say what are the relations with reference 

 to which they are alike, for the stability 

 of species and the mutability of species are 

 not two facts, nor the same fact from two 

 points of view, but two narrow and imper- 

 fect views of the same fact. 



Thus, for example, individual sheep are 

 alike for certain purposes of the zoologist 

 and the paleontologist. They are alike to 

 the embryologist and to the anatomist, and 

 to the physiologist, so far as these scien- 

 tific students are not concerned with their 

 differences. They are, no doubt, alike to 

 the hungry wolf, and to the geese that 

 graze in the same pasture— to their com- 

 petitors and enemies in the struggle for 

 existence. They are alike in their sexual 

 affinity, so far as there is no sexual selec- 

 tion. They are alike in the physiology of 

 reproduction, and in their physiological 

 activity in general, so far as they do not 

 differ in fertility and in constitution. On 

 the other hand, they are different to the 

 stock-breeder, and to the shepherd, to the 

 shepherd's dog, to their lambs, and, no 

 doubt, to each other. 



As we learn more about sheep, we learn 

 more about their identity and more about 

 their diversity, but this does not show that 

 the identity and diversity are in us and 

 not in nature. It only shows that neither 

 the identity nor the diversity has any inde- 

 pendent existence in nature abstracted 

 from the living beings. 



16. Are inheritance and variation tivo 

 processes, or two partial and. imperfect 

 views of the same process? 



