i^i'"^] Goodspeed: Nicotiana Hybrids 175 



cells of hybrids and their chance recombination in later genera- 

 tions" (Hayes, 1912, p. 28) does take place. In 1909 I think 

 it may be safely stated that, broadly speaking, the "unit-char- 

 acter ' ' conception had become ' ' an inseparable attribute of Men- 

 delian inheritance. ' ' The literature dealing with the problems of 

 heredity had become so permeated with the unit-character 

 criterion that it was difficult to discuss a hybridization experi- 

 ment Avithout reference to the more distinct morphological or 

 physiological attributes of an organism by the use of this term. 

 At the present time we are led to believe that there are no "unit- 

 characters" in the sense of "units distinct and indestructible 

 which may meet in fertilization but separate again at the forma- 

 tion of gametes" (Castle, 1911, p. 38). Such an attitude may 

 be one which is entirely in harmony with the progressive spirit of 

 the times — i.e., the rapidity with which speculation along Men- 

 delian lines has swept us forward. 



The question concerning the "relative constancy of unit-char- 

 acters," perhaps because of "its illusiveness" and certainly be- 

 cause the experiment was undertaken in the belief that unit-char- 

 8.cters were "transmitted as independent units in inheritance" 

 (Darbishire, 1911, p. 216), has certainly taken on "a perennial 

 habit" (East, 1912, p. 644) with reference to the behavior of 

 flower size characters in N. acuminata hybrids. The occurrence 

 of interesting and seemingly important evidence on the divisibility 

 of what we may call a strictly "physiological unit-character" to- 

 gether with the complexity of the "flower size unit-character" 

 problem was the occasion for the preparation of a note on the 

 present status of the unit-character conception which was going 

 to press when Professor East's recent paper (Amer. Nat. 46, 551, 

 p 663) came to hand. While it is recognized that the greater 

 part of the whole situation has been reviewed and commented 

 upon by East (loc. cit.) and Castle (Amer. Nat., 46, 546, p. 352) 

 it seems nevertheless advisable to present a brief outline of the 

 above mentioned note together with such experimental evidence, 

 bearing immediately on the subject in hand, as was therein con- 

 tained. 



It was pointed out that ^lendel chose the experimental 

 material ns(^(l in the most famous experiment with a view dimbl- 



