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THE AMERICAN NATURALIST [Vol. XLIX 



hypothesis of De Vries, let us be on our guard between 

 fact and opinion, between natural and unnatural phe- 

 nomena. That the saltation of characters occurs very 

 frequently in plants and in animals under artificial con- 

 ditions there can be no doubt; yet the mass of existing 

 evidence is from artificial rather than from natural 

 sources. 



The recent opinion of Bateson, 17 who by his advocacy 

 of discontinuity in the origin of all specific characters 

 would be predisposed to favor the saltation theory held 

 by De Vries, is partly negative. 



The evidence for the appearance of mutations of higher order, 

 by which new species characterized by several distinct features are 

 created, is far less strong, and after the best study of records which I 

 have been able to make I find myself unconvinced. ... In so far as 

 mutations may consist in meristic [i. e. numerical] 18 changes of many 

 kinds and in the loss of [germinal] 18 factors it is unnecessary to 

 repeat that we have obtained evidence of their frequent occurrence. 



Negative conclusions have also been reached by various 

 botanists, as, for example, Jeffrey: 19 



1. The Onagraceae are largely characterized by hybrid contamina- 



2. This statement holds with particular force for (Enothera lamarck- 

 iana and other species of the genus (Enothera, which have served as 

 the most important basis of the mutation hypothesis of De Vries. 



7. The mutation hypothesis of De Vries, so far as it is supported 

 by the case of (Enothera lamarckiana, is invalidated. 



I do not know of a single instance where a field observer 

 in mammalogy or in paleontology has recorded a new 

 saltation character which is known to be of any signifi- 

 cance in the evolution of the race. On the other hand, 

 certain field observers of birds (Beebe) and of molluscs 

 (Crampton) are of the opinion that they have discov- 

 ered proofs that certain characters arise by saltation 



it Bateson, William, "Problems of Genetics." Oxford University Press, 

 1913, 250 pp. 



is These [] are insertions in Bateson 's text by the present author. 



i» Jeffrey, Edw. C, "Some Fundament;.! Morphological Objections to 

 the Mutation Theory of De Vries,"' The Am Kit. Naturalist, Vol. XLIX, 

 No. 577, Jan., 1915, pp. 5-21. 



