16 CONTACTS WITH DARWINISM I [ch. ii 



often also the species, had any adaptational value whatever, and 

 the higher that one went in the scale, from species upwards, the 

 more difficult was it to find such a value. This, when one comes to 

 think it over, is really a very puzzling fact — why should the 

 differences become larger the higher one goes? Is the struggle for 

 existence greater among the higher groups, between two families 

 for example, than between two species, and between these than 

 between two individuals? A glance at the table of family 

 characters, given as Appendix i, will illustrate this. 



This list of the important characters that distinguish families 

 from one another is after all not so very large. Each family has 

 something to show under most heads. In any pair of allied 

 families that may be taken, there will be mutual agreement in 

 many characters, but a contrasting difference in others, one 

 character of a pair being taken in preference to the other, and 

 that character tending to be shown right through the family, 

 though there are nearly always exceptions in the larger families, 

 the number of exceptions tending to rise with the size of the 

 family. Most of the pairs of characters that are given are such 

 that they do not admit of intermediates, and this divergence of 

 variation, as it is called, is constantly to be found in nature 

 between organisms that are so alike in most of their characters 

 that they are evidently allied in descent. Divergent differences 

 may show between one species and the next, between one genus 

 and the next, as with the berry-fruited Cucubalus in Caryo- 

 phyllaceae, between one tribe, sub-family, or family and the 

 next. As one goes downwards in the scale from family characters, 

 one finds more and more characters coming into use, but they can 

 still very often be arranged in divergent pairs. 



One does not find (usually it is impossible) intermediates be- 

 tween the two characters of a pair, except in a few like superior 

 and inferior ovary, where semi-inferior is possible. But to imagine 

 intermediates between alternate and opposite leaves, or between 

 most of the pairs given, is to ask too much of selection. These 

 characters must, one would imagine, be the result of some sudden 

 change, which would give one or the other. 



The individual characters are so divergent from one another in 

 each pair that it is clear, as in fact has long been well enough 

 known, that variation is definitely divergent. This was always, as 

 Guppy has said, a worry to Darwin, for it was extraordinarily 

 difficult to understand how an evolution, working "upwards" 

 through the variety and species, could drop out at each stage the 



