Xo. 642] VARIATION IN INDIVIDUAL GENE 49 



teriologists, physiological chemists and physicists, simul- 

 taneously with being zoologists and botanists? Let us 

 hope so. 



I have purposely tried to paint things in the rosiest 

 possible colors. Actually, the work on the individual 

 gene, and its mutation, is beset with tremendous difficulty. 

 Such progress in it as has been made has been by minute 

 steps and at the cost of infinite labor. Where results are 

 thus meager, all thinking becomes almost equivalent to 

 speculation. But we can not give up thinking on that 

 account, and thereby give up the intellectual incentive 

 to our work. In fact, a wide, unhampered treatment of 

 all possibilities is, in such cases, all the more imperative, 

 in order that we may direct these labors of ours where 

 they have most chance to count. We must provide eyes 

 for action. 



The real trouble comes when speculation masquerades 

 as empirical fact. For those w^ho cry out most loudly 

 against " theories " and hypotheses "—whether these 

 latter be the chromosome theory, the factorial " liy]ioth- 

 esis," the theory of crossing oxci-, oi- ;niy otlicr -arc 

 often the very ones most .u'uilty of >t;ititiii- tlicir rt-iilts 

 in terms that make illo.ii-itimntr impHcil a>suin])tions, 

 which they themsclvc- ;nv -.arccly aware of simply 

 because they are oppo-cd to .li'auuiiiu' " s]>eculation " 

 into the open. Thus tlicy may bo tiiially UmI into the worst 

 blunders of all. Let us, then, frankly admit the uncer- 

 tainty of many of the possibilities we have di^alt with, us- 

 ing them as a spur to the real work. 



LITERATUEE CITED 



