An Introduction to a Biology 



trial theory of competition. The hybrid, more vigorous 

 than either parent, took the world by storm. We are now 

 witnessing its posterity separating out more or less simply 

 into the two forms which were united in the beginning. Just 

 as every plant in the F x generation contains yellow and green 

 peas, and just as it is not until the next that there can be 

 found plants bearing only yellows or only greens, so Dar- 

 win's interest was in the " Origin of Species by Natural Selec- 

 tion," while now we find de Vries, who is absorbed entirely 

 with the former, and Reid entirely with the latter. . . . 



The experimental method has its limitations no less 

 than its fascination. It is not merely a paradox to say that 

 in biology those things with which we can experiment most 

 are those which to the organism matter least. The reason 

 is that we are not the first to start experimenting. Nature 

 has been there before. For example, the range of continu- 

 ous variation in an organism may either be the direct result 

 of the constitution of the living substance, or it may have 

 been determined by the most stringent selection acting since 

 life dawned. If, therefore, we institute experiments on 

 variation for example, the determination of the effect of 

 heat on the range of variation we may either be studying 

 one of the simple properties of protoplasm or discovering 

 the limits within which natural selection allows the par- 

 ticular organism dealt with to vary under the conditions 

 of heat, e.g., to which we subject it. The really funda- 

 mental processes do not lend themselves to experiment. 

 That is how they have become fundamental. 

 [From a review, Nature, April 4th, 1907.] 



THE PRINCIPLES OP HEREDITY, WITH SOME APPLICATIONS. 

 By G. A. Reid. 1 



The publication of this book marks an epoch in the 

 history of the relation between medicine and biology, inas- 



1 From Nature, December 7th, 190 . 



