82 VARIATIONS, DUE TO REVERSION. 



conjecturally separated, and graduate, as we shall 

 presently see, into each other." 



Now, the only warrant he has for this assertion is, that 

 some changes in an organism, and some varietal types 

 are not due to Reversion. They are not due to Rever- 

 sion, merely because they are negative changes, negative 

 variations, or types which are formed by modifications of 

 the original perfect type of the species to which they re- 

 spectively belong. A cat or dog loses its ear : A pig is 

 modified by the reduction, or the suppression of its tusks, 

 its bristles, its tail, its legs, and its snout : These are the 

 kinds of changes to which he appeals, to show that his 

 unknown causes are operative. He fancies, or affects 

 to believe, that the Fantail pigeon, for instance, cannot 

 be due to Reversion, because the species from which it 

 is known to have descended, has produced varieties 

 with a well developed oesophagus, with length of body, 

 with a long beak, with divergent feathers on the neck 

 and breast, &c. But, it is not the type which has been 

 regained by Reversion, but those positive characters, 

 or features of development, which enter into such 

 types. The feature, fan-tail, is due to reversion. All 

 the positive features of the other varieties of the 

 pigeon, are due to reversion ; the types of those vari- 

 eties are not. There was but one type originally; 

 that type in which is contained all the positive de- 

 velopments of the given species ; and that type alone 

 is perfect. 



Sometimes, it is true, there is a reversion, by an 

 organism, from a positive character, to a negative 

 character. Thus a pig, once under cultivation, has 



