Robertson: Treories of Evolution. 245 
‘but as the recessive character will be masked by the dominant 
one, the DR plants will, to all appearance, resemble DD, so 
that we shall get three apparent dominants to one recessive, 
which is the observed proportion. The fact that these dominants 
are not really all alike, but are made up of some pure dominants 
and some hybrids is shown in the next generation, in. which, on 
Mendel’s theory, the recessive (wrinkled) peas will produce only 
offspring constant to the recessive character, while the dominant 
(round) peas will give rise to a mixture of round and wrinkled. 
The whole thing may be represented diagrammatically :— 
Original parents :— D x R 
First hybrid generation :— D(R) 
zl 
| | | 
1DD : 2D(R) ; 1RR 
| 
| | | 
DD 1DD : 2D(R) : IRR RR 
When the numerical proportions that would be expected on this 
scheme are worked out, it is found that they are closely in 
accordance with those obtained in Mendel’s experimental work : 
from which we may infer that the theory of the purity of the 
germ cells has good claim to rank as a sound working hypothesis. 
“In so far as Mendel’s law applies, therefore, the conclusion is 
forced upon us that a living organism is a complex of characters, 
of which some, at least, are dissociable, and are capable of being 
replaced by others. We thus reach the conception of wzz¢- 
characters, which may be re-arranged in the formation of the 
reproductive cells. It is hardly too much to say that the 
experiments which led to this advance in knowledge are worthy 
to rank with those which laid the foundation of Atomic laws of 
Chemistry.’ * | 
_Mendel’s experiments have been confirmed and extended by 
later workers, and results such as he got have been found to 
hold true very widely both for plants and animals. In plants, 
such pairs of opposed characters as hairiness and glabrousness, 
sugary and starchy endosperm (maize), pinnate and palmate 
leaf-form (Przmula), etc., have been found to fulfil Mendelian 
predictions, as also a great many characters in animals. There 
* W. Bateson. Jr. Roy. Hort. Soc., rgor. 
31907 July * 
