A SUBSPECIES. 



You will recollect that we said classification does not go 

 below species; that the species is the unit of classification. 

 This is very true. But may we not divide a unit ? A sub- 

 species is a fraction of a species. 1 



We can see by a little illustration what is meant, A red- 

 cheeked apple may sometimes be divided so that one half will 

 appear to be entirely red and the other entirely green ; yet 

 when the halves are put together, it is impossible to tell where 

 the green fades and the red begins. Taken separately, we 

 might suppose they were halves of two different apples, but 

 when put together they fit perfectly. It takes both the red 

 and the green parts to make a whole apple. 



As we travel from east to west or from north to south, we 

 shall often find the birds that we. know well singing different 

 songs, showing a different shade of color, or we shall see that 

 they are larger or smaller than the same bird was in our own 

 home. If we were to compare one from the extreme East with 

 one from the far South, we should not believe them to be the 

 same bird, and yet as we travelled we could nowhere say, 

 "These birds to-day are different from those I saw yester- 

 day." There were all possible gradations of color and habit, 

 like that play of color between the red cheek of the apple and 

 its greener side. The change came little by little, as the rosy 

 flush grew on the sunny side of the apple. So we cannot say 



1 These are not given as definitions of species and subspecies, but as con- 

 venient descriptions. As definitions they would " beg the question." 



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