1^0 Arend. L. Hagedoorn and A. C. Hagedoorn. 



we are told that, if we cross a certain white fowl to another black, 

 the two colours blend, the offspring becoming blue. In still other 

 cases we find, that if we cross a white fowl to a black one, the 

 "characters" white colour and black colour form a "mosaic". Now it 

 seems, that a certain class of geneticians is content with such a 

 terminology and with it considers the ultimate goal reached. But 

 there are others, among which we rank ourselves, who are not in 

 the least satisfied by such facts, for whom the real problem does 

 not formulate itself until now. We want to know w/tj in these three 

 cases the result is such a different one, what genetic factors in each 

 case distinguish by their presence or absence the white from the 

 black parent, how many of them we are concerned with, and whether 

 some of the genetic factors concerned, are identical in different blacks 

 or different whites. 



In respect to the actual colours of the fowls observed, it abso- 

 lutely suffices us to state the facts as they are, to say, that in one 

 case a white parent and a black one give blue offspring and so on, 

 and we recognize, that such general names as "partial dominance" 

 ■or "blending inheritance" are unnecessary, and tend to hide all deeper 

 lying problems. Such general names are moreover positively dangerous, 

 for they not only offer a facile way to hide our ignorance of the 

 things which cause the peculiar phenomena observed, but they also 

 assume too much, namely, that the cases which fall together under 

 such a fancy general name, are fundamentally analogous, and this we 

 can never know, without an analytical study of the individual cases. 



Genetics as a science may be likened to Chemistry. In scientific 

 Chemistry we study the elements with all their properties, the effect 

 their presence makes in different combinations of others, and so on, 

 and we can only do so, by observing the properties of compositions, 

 in which they find themselves. But just as there is no direct relation 

 between genes, and the qualities of the organism to the development 

 of which they contribute, so that an organism may contain a gene 

 without ever showing it, so is there no direct relation between a chemi- 

 cal element and the qualities of the compositions into which it enters. 

 It is for this reason principally, that nowadays in Chemistry we do 

 not study the characters of different compounds, their colours and 

 smells for their own sake, but as a means to study more fundamen- 

 tal things. It is just as wrong, to call a gene after some quality of 

 an organism, which it helps to develop, as it would be to call a 

 chemical element after a quality of some compound which it helps 



