SCIENTIFIC FAITH AND WORKS 121 



ologist and the experimental psychologist are already largely physical, 

 and their researches are carried on in laboratories. In proportion as the 

 various circumstances are rendered more amenable to external control, 

 so the methods of biology will more nearly approach those of physics. 

 Whereas biology was until recently chiefly a science of observation, it 

 has now become in a high degree experimental. The physiologist re- 

 moves or alters organs, removes eggs from the natural parent and 

 places them in a foster-mother, cuts off the heads and tails of worms 

 and observes the conditions of survival and regeneration. If the force 

 of gravity were removed, in what direction would a plant grow ? If 

 an egg be subjected to centrifugal force in which direction will the 

 head of the animal appear? These are the sort of questions that the 

 biologist is now attacking. Nor is he without mathematical statements. 

 The great generalization of Darwin of fifty years ago has ever since 

 concentrated attention on problems of development and heredity. Dar- 

 win's conclusions were the results of the observations of a long life. 

 Now the experimental method enables one to hasten and accelerate 

 conclusions. The gentle monk and acute man of science, Gregor 

 Mendel, forty years ago in his cloister at Briinn by his careful experi- 

 ments on the crossing of thousands of peas, and by comparisons of 

 their seeds, flowers and stems, succeeded in unveiling a law which has 

 profoundly influenced ideas on heredity, not only in plants but in 

 animals. He finds that in the process of hybridization there are certain 

 characteristics which are transmitted entire to the offspring, and are 

 termed dominant, others which seem to disappear or become latent in 

 the process, which he terms recessive. When however the hybrids are 

 bred together both qualities reappear in the offspring, and in a definite 

 proportion of three of the dominant to one of the recessive. In the 

 next generation another definite proportion occurs, and so on. We 

 here have a very definite arithmetical relation, which is susceptible of 

 very exact study and confirmation. 



The method of Mendel, which we may call that of experimental 

 evolution, is now of wide application, and there are laboratories which 

 do nothing else but breed and cross under very exact control. Among 

 one of the large-scale experimenters in this line may be mentioned Mr. 

 Luther Burbank, who, though a master of method and subsidized by 

 the Carnegie Institution, seems to be devoted rather to practical than 

 to scientific results. 



In connection with the laboratory or experimental method in evolu- 

 tion, must be mentioned a most promising application of mathematics 

 to biology in the new science of biometrics, or the application of the 

 methods of probability or statistics to great numbers of similar objects. 

 If the doctrines of evolution or of variation are ever to be accurately 

 proved it must be in this manner. To illustrate, suppose we have a 



VOL. LXXVI. — 10. 



