i66 NATURAL SCIENCE. Sept., 



chemical affinity, or gravity, is not a thing to be explained in a 

 formula. We know the positive and negative conditions of its 

 existence ; every month adds to our cataloguing of its phenomena 

 and of its relations to other phenomena. We know nothing but by 

 its qualities, and it is a fair statement to make that science has 

 learned to know as much of the qualities of life as it knows of the 

 qualities of anything. As each step in the slow accumulation of 

 knowledge is made, it will always be open for someone to say, " Ah, 

 my friends, you have discovered America, but how about the North 

 Pole ? " 



Lord Salisbury and Natural Selection. 



Darwinism and the Doctrine of Descent are now in the unhappy 

 position of popularity. Only those who have some practical acquain- 

 tance with the facts involved, with the anatomy and embryology of 

 living animals, and with the history of their fossil remains in the 

 rocks, hesitate to lay down the law for or against what they consider 

 Darwinism. Lord Salisbury's acute mind has avoided the most 

 vulgar error. Since Darwin's solution laid hold of the intelligence of 

 the world and armed it with a new method for the study of organisms, 

 month by month proofs of the doctrine of descent have accumulated, 

 until now no naturalist of position or attainments asserts the 

 immutability of species. But we go beyond Lord Salisbury, and say 

 confidently that there are not six among the well-known biologists of 

 the world who do not hold it as proved that all animals and plants that 

 are alive, or have lived on the earth, are connected with each other 

 by the chain of a common descent. It is upon this achievement that 

 the undying fame of Darwin is based. The dispute about the fact of 

 evolution is over. After the lapse of so many stormy years, the word 

 evolution has earned its right to Lord Salisbury's witty designation 

 " comfortable." It is, as Lord Salisbury rightly said, concerning the 

 method or mechanism of evolution that there is still controversy, and 

 that there may be controversy to the end of time. At the end of the 

 introduction to the first edition of the " Origin of Species," Darwin 

 wrote : — " I am convinced that Natural Selection has been the main but 

 not the exclusive means of modification." At different times after the 

 publication of the " Origin," as may be seen in the different editions 

 of that and other works, Darwin was inclined to attribute sometimes 

 a greater, sometimes a less, important sphere of influence to this 

 factor. At the present time one school, of which Weismann is the 

 leading exponent, believes that Natural Selection, to the exclusion of 

 other factors, is the motive force in evolution. Probably a majority 

 of living naturalists attach to it less importance than did Darwin. 

 But it was because Natural Selection or, " the preservation of 

 favoured races in the struggle for life," furnished an intelligible 

 mechanism for the process of evolution, that Darwin was able to 



