206 A Defence of Mendel's 



nature. In such a case imperfect dominance need not 

 surprise us. 



What we need in all these phenomena is a knowledge 

 of the properties of each race, or variety, as we call it in 

 peas. We must, as I have often pleaded, study the pro- 

 perties of each form no otherwise than the chemist does the 

 properties of his substances, and thus only can we hope to 

 work our way through these phenomena. Ancestry holds 

 no key to these facts ; for the same ancestry is common to 

 own brothers and sisters endowed with dissimilar properties 

 and producing dissimilar posterity. To the knowledge of 

 the properties of each form and the laws which it obeys 

 there are no short cuts. We have no periodic law to guide 

 us. Each case must as yet be separately worked out. 



We can scarcely avoid mention of a further category of 

 phenomena that are certain to be adduced in opposition to 

 the general truth of the purity of the extracted forms. It 

 is a fact well known to breeders that a highly-bred stock 

 may, unless selections be continued, " degenerate." This 

 has often been insisted on in regard to peas. I have been 

 told of specific cases by Messrs Sutton and Sons, instances 

 which could be multiplied. Surely, will reply the supporters 

 of the theory of Ancestry, this is simply impurity in the 

 extracted stocks manifesting itself at last. Such a con- 

 clusion by no means follows, and the proof that it is 

 inapplicable is obtained from the fact that the "degenera- 

 tion," or variation as we should rather call it, need not 

 lead to the production of any proximate ancestor of the 

 selected stock at all, but immediately to a new form, or to 

 one much more remote in the case of some high class peas, 

 e.g., to the form which Mr Sutton describes as " vetch- 

 like," with short pods, and a very few small round seeds, 

 two or three in a pod. Such plants are recognized by their 



