2 CONCEPTS AND DEFINITIONS 



considered a success if it throws light on some of the disputed 

 questions or even if it does nothing more than lead to a more 

 precise phrasing of the basic points of disagreement. 



One way of laying a foundation for such an investigation is to 

 recall some of its history. Who was the first to realize that there 

 is a species problem and what was his proposed solution? What 

 were the subsequent developments? Time does not permit a 

 thorough coverage of the field, but even a glance at the high 

 lights is revealing. If we open a history of biology, the two names 

 mentioned most prominently under the heading of "Species" will 

 be Linnaeus and Darwin. Linnaeus will be cited as the champion 

 of two characteristics of the species, their constancy and their 

 sharp delimitation (their "objectivity" ) . One of the minor trag- 

 edies in the history of biology has been the assumption during 

 the hundred and fifty years after Linnaeus that constancy and 

 clear definition of species are strictly correlated and that one 

 must make a choice of either believing in evolution (the "incon- 

 stancy" of species) and then having to deny the existence of 

 species except as purely subjective, arbitrary figments of the 

 imagination, or, as most early naturalists have done, believing in 

 the sharp delimitation of species but thinking that this necessi- 

 tated denying evolution. We shall leave the conflict at this point 

 and merely anticipate the finding made more than a hundred 

 years after Linnaeus that there is no conflict between the fact 

 of evolution and the fact of the clear delimitation of species in a 

 local fauna or flora. 



The insistence of Linnaeus on the reality, objectivity, and con- 

 stancy of species is of great importance in the history of biology 

 for three reasons. First, it meant the end of the belief in spon- 

 taneous generation as far as higher organisms are concerned, a 

 belief which at that time was still widespread. Lord Bacon and 

 nearly all leading writers of the pre-Linnaean period, except Ray, 

 believed in the transmutation of species and the Linnaean con- 

 ception "of the reality and fixity of species perhaps marks a neces- 

 sary stage in the progress of scientific inquiry." (See Poulton, 

 1903, pp. lxxxiv-lxxxvii for further references on the sub- 

 ject). "Until about 1750 almost no one believed that species were 



