No. 615] INHERITANCE IN PEROMYSCUS 



179 



Much dialectic skill has been displayed in maintaining 

 this set of opinions against the many facts which seem 

 directly to refute them. Indeed, it must be conceded that 

 a fairly consistent and logical edifice has been erected 

 upon these foundations. Strictly logical, though often- 

 times improbable interpretations have been given to each 

 new volley of hostile data, until the fortress has begun 

 to seem impregnable -at least to a frontal attack. 



But perhaps, of late, another metaphor has come to suit 

 the situation better- that of the two knights fighting on 

 opposite sides of the same shield. The Mendelians have 

 recently had recourse to more and more minute factorial 

 differences in explaining certain lesser gradations of 

 color in some of their material, until at length the dis- 

 tinction between their opponent's " continuity" and their 

 own ''discontinuity" is more imaginary than real. 

 Water is a continuous medium for all the ordinary pur- 

 poses of life, and solutions of different substances may 

 be completely 4 'blended" therein. Its resolution into 

 hypothetical molecule.-, atoms, electrons and the like does 

 not in the least affect these fundamental facts. 



The publication of the data which I offer in the present 

 paper confessedly does not constitute a "frontal attack" 

 upon the multiple factor hypothesis. My results belong 

 to a class of facts which have already figured extensively 

 in this controversy, and which have been met by ingeni- 

 ous and plausible counter-arguments. As I have stated 

 elsewhere, I am led to doubt very seriously whether any 

 conceivable evidence could be brought forward which 

 would be admitted by the more extreme neo-Mendelians 

 to be really damaging to their position. As in so many 

 other cases, the victory is to be won, if at all, through 

 a process of "attrition." Positions are gradually aban- 

 doned which are never ills proved in a logical sense. In- 

 deed, as hinted, above, there are clear signs that the 

 defenders of the "multiple factor" explanation of selec- 

 tion and blended inheritance are already retiring from 

 their main positions. 



