PARTICULATE THEORY OF HEREDITY 245 



recent papers (Bates, Riddle, Onslow, Goldsclimidt) that 

 touch on this question it is argued, from the evidence of the 

 specific enzymes supposed or demonstrably involved in 

 the production of some final stage in the chemical reaction 

 that leads to the character in question, that the gene itself 

 is the same specific enzyme. The argument shifts back 

 and forth from unit-character to unit-factor. The reason- 

 able position to take in this matter is, in my opinion, that 

 stated by Loeb and Chamberlain (1915), ^'The hereditary 

 factor in this case must consist of material which deter- 

 mines the formation of a given mass of these enzymes, 

 since the factors in the chromosomes are too small to carry 

 the whole mass of the enzymes existing in the embryo 

 or adult. ^' It should not be forgotten, however, that the 

 evidence in favor of enzyme action as the most important 

 developmental process is by no means established, and 

 even were the evidence for this view adequate, the stages 

 between such action and the ultimate chemical nature of 

 the gene may be too great to be cleared at a single bound. 

 Some of the modern work on the chemical composition of 

 the nucleus indicates that extremely complex protein com- 

 pounds may be present in it — even though some of the 

 split products obtainable from it may be relatively simple. 

 It seems to me therefore that it is both premature and 

 highly speculative at present to tie up the genetic evi- 

 dence concerning the genes with hypotheses concerning 

 their chemical composition. I urge this, but at the same 

 time I realize of course that we should endeavor to obtain 

 as soon as possible better knowledge as to the chemical 

 nature of the chromatin. 



Another question concerning the gene, that has been 

 raised, is whether it is to be regarded as something having 

 a definite molecular constitution, or whether the gene is to 

 be regarded as a quantity of material fluctuating about a 

 mode — its definiteness representing only a general ten- 

 dency for the same frequency distribution to recur in 

 each species. From the nature of the case such a question 



