388 BOTANICAL GAZETTE [November 



Mendelian expectation upon keener analysis of the characteristics involved, and 

 it seems early for the formulation of a law to accommodate exceptional cases until 

 hypotheses are exhausted for making them conform to laws now so fully demon- 

 strated as those of ^Mendel. There is no necessity for the assumption that there 

 is an all-inckisive law of heredity, and it seems probable that there may be a 

 number of more or less independent laws of greater or less inclusiveness which 

 separately or conjointly may explain each single instance of inheritance. Some 

 evidence exists that "variable potency" may represent a fact, but so far as the 

 evidence goes, this fact is of much smaller significance than the segregation of 

 pure gametes. Indeed it is conceivable that variations in potency may be due 

 to several or many different causes, and that it does not represent a sufficiently 

 unified series of phenomena to warrant its designation as a law. 



Cook:^ in discussing Davenport's lecture attempts to classify various methods 

 of descent, and limits "Mendelism" to cases of complete dominance, quite 

 ignoring the feature of Mendelism now everywhere recognized as the most impor- 

 tant, namely, the segregation of pure gametes. In the literature of Mendelism 

 valid explanations of phenomena have been given belonging to most of Cook's . 

 categories, and it seems not unlikely that Mendelian explanation will be found 

 sooner or later for the greater part of the phenomena which Cook classes under 

 polar inheritance. The classification as well as the whole paper is academic 

 and represents thinkable conditions rather than actual ones. He attributes 

 polar inheritance, except in the case of dimorphic and polymorphic species, to 

 narrow breeding, but this assumption is as yet unsupported by experimental 

 evidence. The paper is full of misconceptions and misstatements, the reckless- 

 ness of which is in places startling and amusing. "Elementary species" (p. 206) 

 are wrongly defined as the different kinds or castes of dimorphic or polymorphic 

 species, and "heterozygote" (p, 211) is incorrectly limited to those heterozygotes 

 which display novelties, i. e., characters not found in the parents. The tend- 

 encies of the author to construct a peculiar terminology to represent his thought t 

 rather than follow accepted usage is shown in the use of "conjugate" with the 

 same meaning as the word "zygote," now universally adopted by experimenters 

 in this field. Failing to grasp the possibility that any character may be made 

 up of two or more factors, he is led to the startling conclusion (p. 220) that it 

 is possible for germ cells to transmit characters for many generations without 

 bringing or tending to bring them into expression, and that the Mendelian "laws 

 of disjunction," "purity of gametes," "alternative inheritance," or whatever they 

 may be called, become at once superfluous and inadequate. 



His statements regarding mutations are all academic and mostly without 

 any experimental support. Thus, he says (p. 199), "If the narrow breeding be 

 carried on with persistence, mutative reactions toward greater diversity will 

 appear, and these sudden deviations from an established heredity are even more 



I 



( 



8 Cook, O. F., Mendelism and other methods of descent. Proc. Wash. Acad. 

 Sci. 9:189-240. 1907. 



