182 INHKRITA^X'E, FERTILITY, AND SEX IN PIGEONS. 



interpreted them, seemed to indicate that specific characters behave as "pure" 

 and "independent" units. Mendel's results are now being tested in various forms, 

 and it remains to be seen whether he discovered any principle that admits of uni- 

 versal application. So far as my own work goes, I may say I find no evidence of 

 independent unit-characters, and I think that I find abundant evidence that specific 

 characters do not pre-exist in germs, either as specific units or as determinants. 

 In fact, the whole conception of characters as unit-entities seems to me utterly 

 incompatible with what we know of their genesis and history. 



It is quite true that as yet we have not seen very much serious work on the 

 genesis of characters. It is very much easier to compile ponderous volumes of 

 reported saltations and discontinuities than it is to trace these appearances to 

 their genetic foundations. The criticism I should make of Mendel's work would be 

 that he did not first study with the utmost care the nature of the characters with 

 which he proposed to experiment. 



Furthermore, the claim that any two characters in closely related varieties of 

 peas should be "mutually exclusive" borders on the incredible, and stands in 

 contradiction, as it seems to me, with the very general phenomenon of blending. 

 The conception of characters as indivisible unit-entities seems utterly irreconcilable 

 with all we know of the phyletic derivation of organs and characters. The "prin- 

 ciple of change of function," developed so ably by Dohrn in 1875, shows that 

 characters are only local differentiations that arise by slowly modifying processes. 



The contrary assumption is the negation of evolution, and opens the way to 

 the realm of miracle. There can be absolutely no hope of ever tracing the genesis 

 of characters from the standpoint of Mendelian purity. We may get allelomorphs 

 within allelomorphs ad mfinitum, but every "within " hides the truth we are seeking, 

 in essentially the same way that the old preformationists hid one miracle within 

 another in the womb of mother Eve. (Z 6) 



Some further data and conclusions bearing upon the preceding theme, and 

 written mostly after the above, have been seriated and given a concluding position 

 in this chapter by the editor:^ 



Mendel emphasized the importance of using safe material, but he overlooked 

 the fact that his peas were closely related varieties, which fact may have some- 

 thing to do with alternative mheritancc. Darwin and others have used domestic 

 species. 



"It is willingly granted that by cultivation the origination of new varieties are acquired which, 



under natural conditions, would be lost Various experiments force us to the conclusion 



that our cultivated plants, with few exceptions, are members of various hybrid series,' whose further 

 development in conformity with law is changed and hindered by frequent crossings inter se. The 

 circumstance must not be overlooked that cultivated plants are mostly grown in great numbers and 

 close together, which affords the most favorable conditions for reciprocal fertilization between the 

 varieties present and the species itself." 



The great variability of cultivated plants is, according to Mendel, due not so 

 much to "simple transference into garden soil" as to the cross-breeding which is 

 thus favored and which is systematically practised by the horticulturist. 



' All that follows was written at intervals, and more or less disconnectedly, by Professor Whitman. The editoi 

 is responsible for the order and arrangement of the material. 

 ' The itaUcizing is our own. 



