440 ANNALS NEW YORK ACADEMY OF SCIENCES 



lous flowers of Begonia frigida, formerly described, though they appear fit 

 for fructification, are sterile." ^ The last point, however, does not invali- 

 date the claim to this new type of Begonia as a mutant, since the facts which 

 determine its position in this regard are, first, the sudden appearance of the 

 form bearing three kinds of flowers and, second, the production by seed of 

 descendants also bearing three kinds of flowers. 



It is very evident that this case troubled Mr. Darwin, for he referred to 

 it a number of times and did not relish Professor Harvey's assertion that 

 "such a case is hostile to the theory of natural selection, according to which 

 changes are not supposed to take place per saltum," and Harvey's further 

 declaration that "a few such cases would overthrow it (natural selection) 

 altogether." ^ Sir Joseph Hooker attempted to exjilain the matter so as to 

 weaken Professor Harvey's argument against the doctrine of natural selec- 

 tion, but Darwin himself wrote Hooker saying : 



"As the 'Origin' now stands Harvey is a good hit against my talking so much 

 of the insensibly fine gradations; and certainly it has astonished me that I should 

 be pelted with the fact that I had not allowed abrupt and great enough variations 

 under nature. It would take a good deal more evidence to make me admit that 

 forms have often changed by saltum." 



About the same time, namely early in 1860, Darwin wrote to Lyell on 

 this subject, saying: 



"It seems to me rather strange; he (Harvey) assumes the permanence of mon- 

 sters, whereas monsters are generally sterile and not often inheritable. But grant 

 this case, it comes that I have been too cautious in not admitting great and sudden 

 variations." ^ 



There is an added point of interest about this discussion in the fact that 

 it is the earliest record in print of the consideration of saltation or mutation 

 by Mr. Darwin. 



You have doubtless noticed Mr. Darwin's protest against the belief 

 in the occurrence of important changes "per saltum." He uses this expres- 

 sion with disapproval a number of times and yet his condemnation of the 

 idea involved is not entirely unqualified, as is shown by the following signifi- 

 cant statement : 



"On the theory of natural selection we can clearly understand the full meaning 

 of the old canon in natural history, "Natura non facit saltum." This canon, if we 

 look to the present inhabitants alone of the world, is not strictly correct; but if we 

 include all those of past times, whether known or unknown, it must on this theory 

 be strictly true." * 



1 " Animals and Plants under Domestication," 1st ed., Vol. II, p. 166. Also ibid., 2d ed.. 

 Vol. II, p. 150. 



2 " Life and Letters," 1886, Vol. II, p. 274. 



^Ibid., p. 275. Also, "More Letters," 1903, Vol. I, p. 141. 



■> "Origin of Species," 6th ed., p. 166. See also ibid., pp. 156, 234, 414. 



