Varietäten, Descendenz, Hybriden. 633 



Gates, R. R., Oa the nature ofmutations. (Journ. of Heredity 

 VI. p. 99-108. 1915.) 



From the facts, presented in this paper as to Oenothera- 

 mutations, f. i. O. lata, O. gigas, O. rubricalyx and O. rubrinervis, 

 the writer draws foUowing conclusions regarding the nature of 

 mutations: 



1. Mutations are of many kinds and in many directions. 



2. Evolution is not due, as ßateson and others have urged, 

 to the loss of factors or inhibitors from the germ plasm, but 

 mutations furnish abundant material for real evolution, in which 

 the modification of characters, and divergences in many directions, 

 have occurred. There is really no more reason for supposing 

 evolution to have resulted from "loss of inhibitors" from the germ 

 plasm than there is for the embryologist to assume that the egg 

 develops into a chick by throwing off inhibitors during ontogen\^ 

 This type of embryological speculation was supplanted centuries 

 ago by the observed increase in coraplexity and structure during 

 development of the individual. 



The evolutionary conception of loss of factors and inhibitors 

 has been founded upon the Mendelian characters cannot be gainsaid. 

 But as soon as it is applied to evolutionary conceptions it leads to 

 an erroneous point of view. It is safe to conclude that even apparent 

 losses, such as the origin of recessive white varieties from colored 

 varieties of plants and animals are not realh^ due to the loss of 

 any particle from the germ plasm, but to a chemical (probably in 

 some cases stereochemical) modification in one element of the germ 

 plasm, viz: a chromosome or a portion of one. 



3. Finall5^ another generalization should now be seen to follow 

 clearly from such facts as those mentioned in this paper, namely 

 that the inheritance of any character depends to some extent upon 

 the nature of the character. In other words, the manner of inheritance 

 of an}'' character is determined, or at any rate limited, b}' the 

 manner of its origin. i. e. by the nature of the germinal change by 

 which it appeared. Just as there are different types of discontinuity 

 in Variation, so there are various methods of inheritance of the 

 differences which thus arise. These methods of inheritance naturally 

 depend upon the basic nature of the original change. 



M. J. Sirks (Haarlem). 



Hayes, H. K., Tobacco mutations. (Journ. of Heredit3^ VI. 

 p. 73—78. 1915.) 



"New types in supposedly homozj'-gous material, which sud- 

 denly appear and cannot be explained by crossing, are known as 

 mutation." 



In accepting this definition of mutations, the writer discusses 

 in this paper some "mutations", occurring in different tobacco cul- 

 tures, viz. in Connecticut Cuban Shade tobacco and Connecticut 

 Havana tobacco. The history of the first mutation is described in 

 detail: the original crops consisted of plants with 14 to 25 leaves, 

 and 19,9 leaves as mean, a number that during the 3^ears 1910 to 

 1914 has not changed. A total of 832 plants was counted, the smal- 

 lest number of plants grown in any generation being 124 and the 

 largest number 210. Increasing the average leaf number b}^ the 

 continuous selection of fluctuations proved to be impossible. But in 

 1912 a remarkable "mutation" was found in a field of Connecticut 



