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THE AM ERIC AX XATURALIST [Vol. XL VIII 



The existence of unit characters in the De Vriesian sense does not 

 appear to have been as clearly demonstrated as that of alternative in- 

 heritance . . . and the interpretations are at great variance. Thus, one 

 group of authors [reference made to Bateson, Doncaster, and Tower] 

 recognize characters in organisms that can lie replaced by other char- 

 acters when the proper crosses are made, . . . while on the other side 

 there are those [references to Whitman and Montgomery] who believe 

 that the organism as a whole is the only unit and that there are no 

 actual unit characters. 



Again he says (p. 169) : 



No character of one parent species is ever replaced in the F, hybrid 



are represented in the F, hybrid. It follows then that these grass- 

 hoppers do not exhibit characters which by crossing can be replaced by 

 other different characters; the whole pattern appears to be the only 



There is no real conflict between "Whitman's idea and the 

 accounts given by students of Mendelism, for the latter realize 

 that far-reaching somatic effects may result from a single factor, 

 and the composite character of the hybrid is not an uncommon 

 occurrence. Nabours identifies a particular pattern with the 

 "organism as a whole.'' but since his evidence relates here to 

 color patterns only, nothing is n-ained by the introduction of such 

 a vague phrase as the ''organism as a whole." Specifically he 

 shows that the hereditary differences between any two types can 

 be explained on the assumption of a single differential for each 



With reference to the antithesis presented by Nabours, it must 

 be recognized that the modern literature of Mendelian heredity 

 affords innumerable instances where two or more characters 

 entering from one parent and their allelomorphs from the other, 

 reappear in the F 2 generation in new combinations. 



If we assume with Nabours that each of the eight color patterns 

 are represented by a characteristic condition of the "germinal 

 material," we may use his terms A, B, C, D, E, F, H or I to 

 symbolize this "germinal material" for the various color 



for.l is represented sin, plv bv .1. and' a hvbrid between .1 and B 

 by AB. In ordinary usage, the homozygous form would be 

 represented as A A and its germ cells by A. This is a minor 

 matter. Ordinary usage has the advantage of being more 

 consistent. 



According to Nabours, then, A mated to B gives AB; B mated 

 to F gives BF; C mated to E gives CE, etc. In gametogenesis 

 these factors segregate, so that, for example, BA gives germ cells 



