Varietäten, Descendenz, Hybriden. 517 



rally a small ridge, because one variety was larger than the other. 

 When one of these apples was cut open the flesh was found to be 

 different in texture and flavor in the two regions. Underneath the 

 russet skin the flesh was coarser grained. One end of the apple 

 was distinctly sour, the other insipid, almost sweet. The line of 

 demarcation of the flesh was also sharp. 



In the apples figured the chimera, according to the writer, 

 would seem to be sectorial rather than periclinal, if the line of 

 demarcation ran lengthwise of the apple rather than across it. But 

 as it is, they resemble more a periclinal chimera which has everted 

 its deeper lying tissue at the blossom end of the fruit. The writer 

 asks these questions: "Does the fruit of the apple develop in that 

 way? Will such fruits give us a clue to the answer?" 



M. J, Sirks (Haarlem). 



Castle, W. E., Pure lines and selection. (Journ. of Heredity. 

 V. p. 93—97. 1914.) 



For the practical breeder selection has always some result, 

 while for the biologist selection within the pure line is without effect. 

 The writer gives in this paper his ideas about the practical idea of 

 the stock breeder and the theoretical ideal of the biologist. The 

 biologists pure line would be an imaginary thing, as the mathema- 

 than tical circle; it has no more relations to actual animalsandplants 

 the maihematical circle has to the circles described by the most 

 accomplished draftsman. The author believes that the pure linc 

 Postulates are these two: 1. The effects of environment are not 

 inherited and 2. Inherited characteristics do not vary. 



The first postulate Stands, if not proved, at least not disproved. 

 The second postulate of the pure line theory is a much shakier one; 

 the writer qualifies his "characteristics" as "the ultimate factors of 

 inheritance". The assumption that many independent Mendelizing 

 Units or factors are concerned in the inheritance of size, is not bene- 

 fiting the pure line theory, unless we suppose further that these 

 hypothetical factors do not vary. "But this is an assumption wholly 

 without Warrant. For in all cases studied critically with reference 

 to the constancy of characters demonstrably Mendelian, the cha- 

 racters have found to be inconstant and subject to modification by 

 selection". The writer cites in supporting his manner of view the 

 researches of Calkins and Gregory, showing that the asexual 

 "pure lines" that Jennings obtained in his cultures bf Paramae- 

 cium do vary, lines may be isolated from a Single "pure line" which 

 differ in size from each other more than the "pure lines" of Jen- 

 nings. The budvariations of botanists are also changes occurring 

 within a "pure line" asexually produced and of the same nature as 

 those which arise in the course of sexual reproduction. The argu- 

 ments brought in favour of the pure-line-theory by the Hagedoorns 

 (strong resemblance between heads of wheat of 50 years ago of the 

 present day) are wholly insufficient to support the theory. The last 

 words of this paper are: "Let him wo thinks selection ineffectual 

 try it on any character of any animal. If he is persistent and criti- 

 cal in his experiments, I am confident that he will be convinced 

 of the effectiveness of selection as all practical breeders are, and 

 will thenceforth regard "pure lines" as purely imaginär}^". 



M. J. Sirks (Haarlem). 



