WHAT IS THE ORIGIN OF SPECIES? 1 8/ 



answer in each case was, they are the natural properties of the 

 species. 



The Idea of Mutability at the Foundation of the Discussion of the 

 Origin of Species. — Thus we see that the attachment of the 

 idea of mutability to organic species naturally led to the 

 inquiry as to the origin of the properties or distinguishing 

 marks of different species; and still further, it led to the dis- 

 sociation of the characters from the species, causing them to 

 be considered separately. The difference in point of view is 

 a radical one, and the great amount of dispute and contro- 

 versy which has resulted may be traced in great measure to 

 the radical difference of meaning which the two schools 

 attached to the word species. To a naturalist of the older 

 ideas it was as absurd to speak of the origin of species as to 

 speak of the origin of gold ; both of these were supposed to 

 occur in the world naturally, and that was enough. 



What is Mutable? — When we speak of mutability, then, we 

 ask, " What is it that is mutable?" Physiologically, the muta- 

 ble element about species is the steps of the development ; that 

 is, there is not a perfect fixity of the law of development of 

 the offspring when it starts upon its individual career as an 

 embryo. Morphologically, the mutable characters of the 

 species are among the most unimportant of the characters it 

 assumes; for each individual of the species they are called its 

 varietal characters. 



A Concrete Example ; Its Characters Symbolically Represented. 

 — In order to fully answer the question what is mutable, 

 and therefore what is it that is evolved in the course of the evo- 

 lution of a new species, we are obliged to consider a concrete 

 case. We must take an actual individual specimen of a 

 particular species, and ask. What is it about this specimen 

 organism which is mutable and has arisen by the evolutional, 

 as distinct from the developmental, processes of the individual 

 growth ? 



Such an example, whatever it be, has numerous characters 

 which are recognized by the systematic zoologist, and are 

 defined by him under separate heads arranged in the order of 

 rank, the whole constituting the taxonomic definition of the 

 particular species. To express the relation of these characters 



