578 CLARENCE E. McCLUNG 



seeking parallels between elements of structure and action in the 

 chromosomes, and the mass effect of cellular action as exhibted 

 in the so-called body characters. Such a method is justified by 

 all our other experience in tracing relations between structure 

 and function in organisms, and while it apparently resolves the 

 individual into parts of greater or less independence, has given 

 us our best conceptions of it as a whole. Homologies have been 

 much more significant of relationship than analogies when con- 

 cerned with organic parts, and I do not doubt that conclusions 

 drawn from structural relations will greatly exceed in value the 

 remote and equivocal analogies between nuclear structure and 

 colloidal phenomena. On the basis of our experience we antici- 

 pate a commensurate relation between structure and function, 

 but this does not mean a fixed and exclusive correspondence — 

 it docs not signify that a function necessarily entirely lapses in 

 the absence of a certain structure. All our observations indi- 

 cate that the relatively few functions of the living substance — 

 irritability, contractihty, metabolism and reproduction — are 

 shared by all its parts in varying degrees, and when we speak of 

 the function of any somatic organ or cell part we mean its 

 outstanding and preponderant activity. 



With this understanding of the relation between morphology 

 and physiology, we speak of the chromosomes as having to do 

 with the process of reproduction, and conceive of them as 

 non-homogeneous within themselves and individually unlike. 

 In this sense they bear factors, or have parts, which are most 

 concerned with certain peculiarities which, through cumulative 

 action in cell reproduction, come to fullest expression in regions 

 of the complete soma. Through what manner a factor operates 

 to produce a cell structure which, in a given cell aggregate, 

 summates in the form a somatic character, we do not know, 

 and that is not the question immediately at issue in the indi- 

 viduality hypothesis. What is postulated there is that the 

 chromosomes are self perpetuating entities with individual pecu- 

 liarities of form and function to identify them. Characteristics 

 of form and behavior we see; certain very definite parallels be- 

 tween these and the manifestations of somatic characters exist 



