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The Journal of Heredity 



an existence of which this disjunction 

 would be the last term" (p. 14). He 

 then refers to Naudin's case of disjunc- 

 tion in Datura, which is elsewhere 

 discussed. Verlot's expression of views 

 on the matter of methods of selection is 

 so thoroughly typical of the thought of 

 his time, i. e., that variation is in conse- 

 quence of the "breaking up" of the 

 "type," and that selection, ipso facto, 

 intensifies the variation in the direction 

 selected for, that it is a matter of 

 interest to present here the view ex- 

 pressed. "If a variation is produced 

 in a direction other than that toward 

 which one tends, it ought not to be 

 abandoned for that; one will have more 

 chance of obtaining new variations in 

 sowing a deviation from the type, even 

 in a diametrically opposite direction, 

 than in sowing anew the type itself. 

 In the deviation there is already a 

 tendency toward perturbation, and to- 

 ward the beginning of the destruction of 

 atavism" (p. 31). 



Another interesting example of the 

 older empirical point of view regarding 

 plant improvement is Vilmorin's opinion, 

 quoted by Verlot, and which is here 

 reproduced to show how thoroughly 

 the primary idea of "breaking up the 

 type" in order to bring about "varia- 

 tion" entered into the thought and 

 operations of pre-Mendelian breeders. 



"To obtain from a plant not yet 

 modified, varieties of a kind determined 

 in advance, I will first set myself to 

 making it vary in some direction or 

 other, choosing for the reproducing 

 factor, not that one of the accidental 

 varieties which would most nearly 

 approach the form which I have pro- 

 posed to myself to obtain but simply 

 that which would most differ from the 

 type. In the second generation, the 

 same care would make me choose a 

 deviation, the greatest possible at first, 

 the one most different, in a word, from 

 that which I would have chosen in the 

 first place. Following this direction for 

 several generations, there necessarily 

 ought to result, in the products obtained, 

 an extreme tendency to vary ; there then 

 results again, and that is the principal 

 point according to me, that the force of 



atavism, exerting itself counter to very 

 divergent influences, will have lost a 

 great part of its power, or, if one ven- 

 tures to make use of this comparison, it 

 will exert it always in a broken line" 

 (p. 28). 



Man's relation to the fixation of 

 characters in new races of plants is 

 stated by Verlot in the usual manner 

 prevalent in the days before Mendelian 

 analyses: "In brief, gardeners have re- 

 marked with reason that a plant newly 

 introduced is very susceptible to vary. 

 This fact, it is conceived, has nothing 

 surprising about it. It confirms that 

 which we have previously said, that a 

 variety, whatever it might be, had need, 

 in order to become fixed, of being cul- 

 tivated for a greater or less length of 

 time, until one had finally come to 

 maintain with it the tendency not to 

 depart from being that which he had 

 made it" (p. 70). 



In other words, the idea then preva- 

 lent, and more or less incoherently 

 expressed, was that, in some unknown 

 manner, man, by continued selection, 

 succeeds in impressing upon a "variety" 

 the stamp of a certain type, and, through 

 repeated and continuous selection in the 

 same direction, finally "fixes" it, so 

 that the variety becomes, as it were, 

 stabilized. Analyzed in a modern way, 

 it simply means that, by continuous 

 selection of some certain type, those 

 individuals are usually isolated which 

 are homozygous for the character-units 

 thus represented, and which become 

 "fixed," because no heterozygous factors 

 are left to split apart. 



We have here, in other words, an 

 unscientific sensing through practical 

 experience of the fact which the breeder 

 of today would define as the selection of 

 a heterozygote having dominant charac- 

 ters differing from those of the species. 

 Being of hybrid nature, such a plant 

 would break up and hence yield new 

 types, whereas the plants resembling 

 the type are more apt to be homozy- 

 gous and less liable to vary in their 

 progeny. He emphasizes the view just 

 set forth still more emphatically in the 

 following words: "If two variations are 

 produced, of which the one differs little 



