THE AMERICAN NATURALIST [Vol. L VI 



III. A Possible Attack thkough Chromosome Behavior 

 In thus recognizing the nature and the importance of 

 the problem involved in gene mutability have we now 

 entered into a cul de sac, or is there some way of pro- 

 ceeding further so as to get at the physical basis of this 

 peculiar property of the gene! The problems of growth, 

 variation and related processes seemed difficult enough 

 to attack even when we thought of them as inherent in the 

 organism as a whole or the cell as a whole — how now 

 can we get at them when they have been driven back, 

 to some extent at least, within the limits of an invisible 

 particle! A gene can not effectively be ground in a 

 mortar, or distilled in a retort, and although the physico- 

 chemical investigation of other biological substances may 

 conceivably help us, by analogy, to understand its struc- 

 ture, there seems at present no method of approach along 

 this line. 



There is, however, another possible method of approach 

 available : that is, to study the behavior of the chromo- 

 somes, as influenced by their contained genes, in their 

 various physical reactions of segregation, crossing over, 

 di\asion, synapsis, etc. This may at first siglit sccni vci y 

 remote from the problem of gettinu' at the >liu<'tui'al 

 principle that allows mutability in the gene, l)ut L am in- 

 clined to think that such studies of synai)tic attraction l)e- 

 tween chromosomes may be especially enlightening in this 

 connection, because the most remarkable thing we know 

 about genes— besides their mutable autocatalytic powers- 

 is the highly specific attraction which like genes lor local 

 products formed by them) show for each other. A- in 

 the case of the autocatalytic forces, so here the atti ;u'ti\ r 

 forces of the gene are somehow exactly adjust. m1 a- 

 to react in relation to more material of the same . ..in 

 plicated kind. Moreover, when the gene nmtate^, the 

 forces become readjusted, so that they mav now attiact 

 material of the new kind; this shows that tlie at tractive 

 or synaptic property of the gene, as well as its catah tie 

 property, is not primarily dependent on its specific struc- 

 ture, but on some general principle of its make-up, that 



