CHAPTER IX 



Experimental biology continued. The factors of evolution: 

 natural selection, mutation, orthogenesis, isolation, inherit- 

 ance of acquired characters. Experimental modification of 

 the germ cells. 



The search for the beginnings of things was one of the ear- 

 liest tasks of the human mind. Man, like a little child, with 

 a * ' why ? ' ' ever present on its tongue, has never ceased to ask 

 the questions, " Whence came I, and whither am I bound?" 

 With the latter question science, with her present limitations 

 of time and space, has naught to do, but the latter ever has 

 been, and perchance ever will be the focal spot of human 

 thought. Strange and curious are the many fancies with 

 which primitive philosophy has invested the problem, and in 

 spite of all the wonderful achievements of modern science she 

 is still but playing with the pebbles on the seashore. We 

 smile complacently as we read of the fat turtle of the Iroquois 

 philosopher, which, waddling along one hot summer day, 

 found his shell too great a burden, and throwing it off became 

 a man; or of the crude philosophy of the early Greeks who 

 imagined a fish coming upon land, bursting its horny capsule 

 and stepping forth a man ; or yet of the old French philoso- 

 pher who related a tale of a wonderful tree, whose leaves, 

 falling on the one hand upon water, gave rise to fish, and on 

 the other upon land, took wings and flew away as birds, 

 naively remarking that while this magical tree was not, to 

 be sure, to be seen in France, yet it was said to be common 

 in Scotland, a land, which to the reader of those days, was a 

 terra incognita. And we shake our heads learnedly as we 

 talk today of "fortuitous variation/' "internal perfecting 

 principles, " " entelechies " or ' ' orthogenetic evolution. ' ' But 

 when, in the language of the street, we "get down to brass 

 tacks " are we really any wiser than our forbears? And yet 

 the denser our ignorance the more alluring becomes the field 

 of research, while the frontiers of knowledge ever recede as we 

 approach, impelled by the primeval instinct to explore. 



While the theory of evolution has become axiomatic among 

 thinking men of every school, the ways and means of evolu- 

 tion are as great a bone of contention as ever. It is but nat- 



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