( xiv ) 



one ancestral pair of which they had retained practically all 

 the heritable qualities: i.e. they differed only in such respects 

 as we have reason to think either (cr) individual and not 

 phylctic (aberrations, monstrosities), or (l>) phyletic but quite 

 trifling in comparison with the conformity in other points 

 {races, sub-species), or (c) resulting from a potential variability 

 which was itself part of the original inheritance {dimorphism, 

 special adaptations, etc.). He believed that " syngamy " would 

 practically always characterize such a group, but that it was 

 not the character which he himself had most in mind when 

 considering whether a group was or was not a species. Nor 

 did he think the absence of links with other groups essential 

 to the definition. 



Species seemed to him real but not permanent or ultimate 

 phenomena in nature. At any time a transverse section 

 through the " Tree of Life " (Darwin) would show us forms 

 arranged at actual differing distances from one another, 

 but no two such sections taken at different epochs would give 

 the same result. What is now a species will one day be 

 represented by a genus, or it may have passed out of existence 

 altogether. The Systema Naturat seems to conceive Science as 

 mapping out and measuring a stationary field, we have come 

 rather to regard her as having to deal with a flowing river. 



Dr. F. A. DixEY said that though it was easy to define a 

 "species" in the logical sense, the zoological conception of 

 the term was svirrounded by great difliculties. Darwin had 

 explained what he meant by a species in contradistinction to 

 a variety ; but. as Professor Poulton pointed out in his 

 Presidential Address, when asked for a definition by Phillips, 

 Darwin had admitted his inability to give one. It was 

 necessary to have a working unit for purposes of classification. 

 Linna3us had supplied such a unit which had served its 

 purpose for a time, but like other attempts it had eventually 

 been found wanting in correspondence with the facts of nature. 

 The present state of fluidity, however, was more hopeful than 

 the old confusion out of which the Linnjean conception 

 emerged. It implied a recognition of the fact that hard-and- 

 fast lines were not easily, found in nature. Here and there 

 an isolated assemblage of individuals could be named, round 



