448 POPULAR SCIENCE MONTHLY 



true, is an enquiry that does not fall within the limits of zoological 

 science. 



We now come to the second great division of zoology, which as a 

 whole is concerned with broad and deep enquiry into the workings of 

 nature; it is natural history in the best sense. Prior to the time of 

 Darwin attempts to solve the kinetic problems of the organic world 

 were hampered by anthropomorphism and narrowness of view, as well 

 as by paucity of facts. But since then, owing to the immense influence 

 of the works of that great naturalist, so much attention has been given 

 to the fundamental problems of life that it is now possible to correlate 

 many principles which describe not only the fact of evolution but many 

 of the factors as well. And in this modern development wide observa- 

 tion has led so directly to extensive experiment that we may justly 

 characterize the present period as an age of experimental zoology. 

 Just as all the apparently disconnected studies of structural zoology 

 deal with one matter — evolution — so in the sphere of experimental 

 zoology all the radii converge upon the study of the factors and method 

 of species transformation. 



"We can only mention some of the modern departments which have 

 yielded brilliant results, such as cytology, experimental embryology, 

 experimental fertilization and regeneration. But we may point out 

 that the general problems in these various fields deal like the problem 

 of evolution itself with an analysis of the internal and external influ- 

 ences that determine the final adult conditions of species. For example, 

 the adult salamander possesses a specific structure, in a state of balance 

 or adaptation, that is the final result of an evolution process up to 

 the present time ; this same specific condition is the goal of the changes 

 through which the salamander's egg and embryo pass in development; 

 it is the goal also that may be reached by even a portion of a divided 

 salamander's egg; while finally it is the goal of the regenerative proc- 

 esses that enable a salamander from which a leg has been cut off to 

 reproduce the missing part. Everything centers then about the ques- 

 tion as to the origin of adult specific forms, which exhibit adaptation. 



Eealizing this, we may pass on immediately to consider how through 

 the study of adaptation, Darwin was led to formulate his potent 

 theories, which have been the basis for recent progress. As the other 

 speakers upon biological sciences have already stated, the most striking 

 feature of animals and plants is their adjustment to their vital con- 

 ditions. An organism that seems so sufficient unto itself, so capable 

 and independent, is nevertheless inextricably interlocked with its sur- 

 roundings, for its very substance is composed of materials which with 

 their endowments of energy have been wrested from the environment. 

 An animal that is pressed upon by the substances of the outer world, 

 that is played upon by various energies, and is attacked on all sides by 



