316 THE ZOOLOGIST. 



disturb us. Quantity is of no account in these considerations. 

 Shakespeare once existed as a speck of protoplasm not so big as a 

 small pin's head. To this nothing was added that would not equally 

 well have served to build up a baboon or a rat. Let us consider how 

 far we can get by the process of removal of what we call " epistatic " 

 factors, in other words those that control, mask, or suppress under- 

 lying powers and faculties. I have spoken of the vast range of 

 colours exhibited by modern Sweet Peas. There is no question that 

 these have been derived from the one wild bi-colour form by a 

 process of successive removals. When the vast range of form, size, 

 and flavour to be found among the cultivated apples is considered it 

 seems difficult to suppose that all this variety is hidden in the wild 

 crab-apple. I cannot positively assert that this is so, but I think all 

 familiar with Mendelian analysis would agree with me that it is 

 probable, and that the wild crab contains presumably inhibiting 

 elements which the cultivated kinds have lost. The legend that the 

 seedlings of cultivated apples become crabs is often repeated. After 

 many inquiries among the raisers of apple seedlings I have never 

 found an authentic case — once only even an alleged case, and this on 

 inquiry proved to be unfounded. I have confidence that the artistic 

 gifts of mankind will prove to be due not to something added to the 

 make-up of an ordinary man, but to the absence of factors which in 

 the normal person inhibit the development of these gifts. They are 

 almost beyond doubt to be looked upon as releases of powers normally 

 suppressed. The instrument is there, but it is " stopped down." 

 The scents of flowers or fruits, the finely repeated divisions that give 

 its quality to the wool of the Merino, or in an analogous case the 

 multiplicity of quills to the tail of the fantail pigeon, are in all 

 probability other examples of such releases. You may ask what 

 guides us in the discrimination of the positive factors and how we 

 can satisfy ourselves that the appearance of a quality is due to loss. 

 It must be conceded that in these determinations we have as yet 

 recourse only to the effects of dominance. When the tall pea is 

 crossed with the dwarf, since the offspring is tall we say that the tall 

 parent passed a factor into the cross-bred which makes it tall. The 

 pure tall parent had two doses of this factor; the dwarf had none ; 

 and since the cross-bred is tall we say that one dose of the dominant 

 tallness is enough to give the full height. The reasoning seems un- 

 answerable. But the commoner result of crossing is the production 

 of a form intermediate between the two pure parental types. In 

 such examples we see clearly enough that the full parental characte- 

 ristics can only appear when they are homozygous — formed from 

 similar germ-cells, and that one dose is insufficient to produce either 

 effect fully. When this is so we can never be sure which side is 

 positive and which negative. Since, then, when dominance is in- 

 complete we find ourselves in this difficulty, we perceive that the 

 amount of the effect is our only criterion in distinguishing the 

 positive from the negative, and when we return even to the example 

 of the tall and dwarf peas the matter is not so certain as it seemed. 

 Professor Cockerell lately found among thousands ol yellow sun- 



