NATURAL SELECTION 101 



The sudden loss of horns brings out a point to which, I think, 

 attention has never been directed in discussions on pammixis. 

 The evolution of new characters is a gradual process requiring 

 ages of time. Geology shows that the stag's antlers have grown 

 step by step from small beginnings. But they might be com- 

 pletely lost in a single generation. The horns of cattle, though 

 less magnificent, are none the less the slow product of ages of 

 unintermitted selection. But by a sudden freak they disappear 

 utterly in an individual here and there, or leave only a dangling 

 vestige attached to the skin. 



Those evolutionists who love symmetrical theories, mapped 

 out regardless of observed facts, imagine a process of retro- 

 gression by which all the stages in the evolution of the most 

 complex animals may be retraced in ordered succession. What 

 actually happens is usually very different. An elaborate organ 

 is suddenly much reduced and mutilated or suddenly disappears 

 altogether. The wing of the apteryx has not become by rever- 

 sion a reptile's fore-limb, then the fin of a primitive fish, and 

 after these transformations slowly dwindled. Under the downy 

 feathers is a minute avian wing, not a reptilian fore-limb or a fin : 

 the machinery of flight has been simply reduced, and, probably 

 not by slow degrees, reduced almost to the vanishing point, so 

 that loss rather than reversion is the word to describe what has 

 happened. No ancestor of the apteryx had a fore-limb similar to 

 the vestige that survives in the present representative of the line. 

 We have here the result of a tendency that is, I believe, 

 universal in the organic world, of heredity tending to fail and 

 let the complex organism that evolution has built up suffer dis- 

 memberment. But when through such failure an incomplete or 

 distorted form arises, Natural Selection usually makes short work 

 of it, and we thrust it from our notice as a thing of no import- 

 ance. If, however, it is not wiped out, the disease, so to speak, 

 may spread to the whole species. 



First, the incompleteness shows itself sporadically in a few 

 individuals, and reversion, a tendency always at work, very 

 probably replaces the lost structure in the offspring. Yet 

 these, though they may seem sound and perfect as a bell, are 



