RECENT ADVANCES IN ANIMAL BREEDING, 135 
The second objection is merely a detailed expression of the first; it 
states in what the limitation lies. Mendel’s law is said to apply to a very 
few characters, of which colour stands out pre-eminently among the rest. 
And although it is true that the list of characters whose inheritance can 
be described in terms of Mendel’s law comprises many other characters 
than colour, e.g. the shape of the comb in fowls, the waltzing habit in 
mice, and even, lately, resistance to disease in plants, it is nevertheless 
true that the number of characters to which Mendel’s Jaw can be said to 
apply is very small indeed when compared with the number of characters 
which go to make up an organism. And it can be said with some truth that 
the characters with which the hybridiser can deal are in a sense superficial. 
When we cross an albino and a waltzing mouse the result is to our eyes 
remarkably different from either parent; it is like a wild mouse, but it 
isa mouse. The features in which it differs from its parents are its 
colour, its progression—it never waltzes like one of its parents—and to a 
certain extent its vigour and temperament, for it is healthier and wilder 
than either parent: but, it is still a mouse. The charge is brought against 
the hybridiser that he can only stir up the surface, but that he cannot 
disturb the depths. My answer to this objection is that it is entirely 
well founded ; that there certainly are two sets of characters, one which 
can be affected by hybridisation, and another, a much larger one, which 
cannot, and that it is legitimate to regard the former as upper and the 
latter as lower. By saying this I do not mean to subscribe to the view 
that recently arisen characters have less tendency to be transmitted than 
old ones. The case of snails will illustrate my meaning. In Helix 
nemoralis the unbanded condition is dominant over the banded. Now, it 
is probable that some form of banding is more ancient than colourlessness, 
and still more probable that some form of colouring at any rate is more 
ancient than colourlessness, yet absence of colour is dominant over colour. 
But my point is that in crossing these snails the only thing affected is 
colour; this is almost true when H. nemoralis is crossed with another 
species, H. hortensis: it is not quite true because the cast of the spire of 
the shell is also altered, but the main thing which is affected is the colour. 
The animal was a snail, a Helix, before it had any definite colour ; and, 
even after it had become stamped as Helix, probably underwent many 
alterations in coloration. I hold that it cannot be denied that the characters 
with which one deals are in this sense superficial. But I do not think 
that this need be regarded as a damaging admission by the hybridiser. 
On the contrary, I hold that the recognition of a limit between the 
two sets of characters—alterable and unalterable—is desirable, and that 
the discovery of the difference between the kinds of characters which it 
separates would be intensely interesting. 
The objection that the Mendelian only deals with hybridisation pheno- 
mena—doubtless very interesting and important phenomena, it is often 
perhaps semi-ironically granted—must be met. Those who urge it com- 
plain, “It is all very well to tell us about hybridisation—about the result 
of the union of unlike; we want to know about the union of like. 
Hybridisation seldom occurs in nature, and when it does the results 
are more perplexing than in the case of crossing domésticated breeds. 
What we want to know is, ‘What is the mechanism by which the 
