5 i6 THE POPULAR SCIENCE MONTHLY. 



fred Russel Wallace, whose masterly works on the " Geographical 

 Distribution of Animals," and on " Island Life," have immense geo- 

 logical as well as biological implications. 



In pure biology, besides the grand advance implied in the establish- 

 ment of the doctrine of descent with modification, and its subsidiary 

 principles of survival of the fittest and sexual selection, profoundly 

 important minor results have also been attained in many directions. 

 Embryology in the hands of Von Baer and his successors, notably 

 Kowalevsky and Balfour, has acquired prime importance as an instru- 

 ment of geological research. Comparative osteology in the hands of 

 Owen, Huxley, Gaudry, and Busk has given us new views of the 

 relationships between vertebrate animals. The pedigree of fishes, 

 amphibians, reptiles, birds, and mammals has been worked out with 

 a considerable degree of fullness from the hints supplied us by the 

 amphioxus, the ascidian larva, the facts of embryology, and the numer- 

 ous recent discoveries of intermediate or arrested organisms, recent 

 and extinct. Invertebrate zoology has been rescued from chaos and 

 partially reduced to temporary and uncertain order. Botany, at once 

 the dullest and the most alluring of all sciences, has been redeemed 

 from the vicious circle of mere classificatory schemes, and vivified by 

 the fresh and quickening breath of the evolutionary spirit. The new 

 morphology has revolutionized our ideas of vegetal homologies ; the 

 new physiology has fastened all its attention on the adaptations of the 

 plant to its natural environment. The fascinating study of the mu- 

 tual relations between flower and insect in particular, set on foot be- 

 fore the dawn of our epoch by Christian Sprengel, but reintroduced 

 to notice in recent times by Darwin's works on orchids and on cross- 

 fertilization, has been followed out with ardor to marvelous results 

 by Hermann Midler, Axel, Delpino, Hildebrand, Lubbock, Ogle, and 

 others. Heer and Saporta have worked out in great detail the devel- 

 opment of several fossil floras. Last of all, Herbert Spencer has cast 

 the dry light of his great organizing and generalizing intelligence on 

 the problems of heredity, genesis, variation, individuality, and the laws 

 of multiplication. Fifty years ago biology was a mighty maze wholly 

 without a plan. To-day the clew has been found to all its main ave- 

 nues, and even the keys of its minor recesses are for the most part well 

 within reach of the enlightened observer. 



Even the actual gains in the number of new organisms added to 

 our lists during the last half-century are in themselves astonishing ; 

 and, strange to say, the species that bear most closely upon the theory 

 of organic evolution are almost all of them quite recent additions to 

 our stock of knowledge. The gorilla appeared on the scene at the 

 critical moment for the " Descent of Man." Just on the stroke when 

 they were most needed, connecting links, both fossil and living, turned 

 up in abundance between fish and amphibians, amphibians and rep- 

 tiles, reptiles and birds, birds and mammals, and all of these together 



