68 



THE AMEBIC AX A. I I CR A Lis T [Vol. XLIII 



tain average for each species or variety, are at times 

 accumulated to such a degree as to carry all the members 

 of the group forward to a new center of oscillation so as 

 to constitute in effect a new group. It was not at first 

 his idea that a single individual, or a small number of 

 individuals, might occasionally develop evolutionary 

 force enough to over-leap suddenly the imaginary bound- 

 ary and become the nucleus of a new colony beyond; 

 that is the substance of the mutation theory; and, while 

 I think it can be shown that Darwin more or less clearly 

 recognized the possibility of the occasional origin of 

 permanent races by this method of saltation, there can 

 be no doubt that he entertained a strong bias in favor of 

 the evolution of species generally by slow and minute 

 steps. 



As far as cultivated plants and domesticated animals 

 were concerned Darwin was willing to grant the widest 

 range of variation and the most abrupt changes, but as 

 to animals and plants in a state of nature he was more 

 sparing of his admissions that great and sudden depart- 

 ures from specific types might occur. This tenure of 

 the two points of view was due to his belief that the 

 domesticated animals and plants were more variable than 

 feral forms because of the direct influence of man upon 

 their surroundings and habits of life. Inasmuch as his 

 theory of the origin of species through natural selection 

 is founded on analogy between the deliberate operations 

 of breeders in choosing the most desirable individuals 

 of their flocks and gardens, and the inevitable sifting out 

 of feral forms through their competition with one another 

 in the struggle for existence, it is difficult to see why Mr. 

 Darwin hesitated about carrying the comparison to its 

 logical conclusion in the admission that what we now 

 call mutations, but what he referred to as "spontaneous 

 variations," "sports," "monstrosities," etc., stand upon 

 substantially the same basis in nature as in cultivation. 

 According to the present-day views of scientific students 

 of animal and plant breeding, I understand, there is no 



