176 



GENERAL EVOLUTIOK 



Fig. 7. 



of growth, can not be distinguished by any common, i. e., generic 

 character, from the individuals of group A, but whose growth 

 has only attained to a point short of that reached by those of 

 group A at maturity. Here we have a parallelism, but no true 

 evidence of descent. But if we now find a set of individuals be- 

 longing to one species, or, still better, the individuals of a single 

 brood, and therefore held to have had a common origin or parent- 

 age, which present differences among themselves of the character 



, in question, we have gained a point. 



' =:: A We know in this case that the individ- 

 uals, a, have attained to the complete- 

 ness of character presented by group A, 

 h while others, b, of the same parentage 

 T> have only attained to the structure of 

 those of group B. It is perfectly obvious 

 that the individuals of the first part of 

 the family have grown further, and, therefore, in one sense faster, 

 than those of group b. If the parents were like the individuals 

 of the more completely grown, then the offspring which did not 

 attain that completeness may be said to have been retarded in 

 their development. If, on the other hand, the parents were like 

 those less fully grown, then the offspring which have added some- 

 thing have been accelerated in their development. 



I claim that a consideration of the uniformity of Nature's 

 processes, or inductive reasoning, requires me (however it may 

 affect the minds of others) to believe that the groups of species, 

 whose individuals I have never found to vary, but which differ in 

 the same point as those in which I have observed the above varia- 

 tions, are also derived from common parents, and the more ad- 

 vanced have been accelerated or the less advanced retarded, as the 

 case may have been with regard to the parents. 



This is not an imaginary case, but a true representation of 

 many which have come under observation. The developmental 

 resemblances mentioned are universal in the animal, and probably 

 in the vegetable kingdoms, approaching the exactitude above de- 

 picted in proportion to the near structural similarity of the spe- 

 cies considered. 



Example 1. — It is well known that the CervidcB of the Old 

 World develop a basal snag of the antler (see Cuvier, " Ossemens 

 Fossiles," and Gray, " Cat. British Museum ") at the third year ; a 

 majority of those of the New World (genera Subulo, Cariacus) 



