130 THE GROWTH OF GROUPS 



The question is, can these groups get a start, can a 

 group containing fifty or so individuals arise from the 

 one or two ? If there are fifty of them in nature they have 

 started and the rest may be easy. The observations 

 among the beetles show conclusively that, given a start, 

 a small group may become a species under natural con- 

 ditions. They do not perhaps show so clearly that a 

 mutant may get a start, but the possibility of its doing 

 so was first clearly demonstrated by Mendel's experiments. 



Among the rats it was the small group of mutants 

 which were particularly in evidence. The groups found 

 at Rangoon and Poona had, so to speak, started, this 

 was certain, and they must, I think, have arisen from one 

 or a few mutants. My own strong belief in the efficacy 

 of mutants arose perhaps in the following manner. I 

 had the benefit of Mr. Tower's observation that given a 

 start the mutant might become a species, and I had also 

 seen among the rats that such startings actually occurred, 

 although the great majority of them come to nothing. 



We are told that there were insuperable difficulties in 

 the path of all the observed mutants of Leptinotarsa. 

 But what if there had been no difficulties ? In that case 

 the sports would not have come before us as such, they 

 would have been species. They appeared as sports because 

 they could not overcome the difficulties. Pallida was only 

 found as a sport, but rulicunda was found both as a sport 

 and as a species ; at Toluca it had overcome the difficulties. 



Different minds pronounce different judgments. Men 

 see alike, but they judge differently concerning what 

 they see. Some, like myself, judge that groups arise from 

 mutants, that is to say they believe that mutants occasion- 

 ally grow into groups. Such occasions must be rare, for 



