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SCIENCE 



[N. S. Vol. XXX. No. 772 



bridge, eleven were British, two American, six 

 German, one Frencli, one Danish and one 

 Dutch. But this is merely an incident. Sci- 

 ence takes no cognizance of state or racial 

 boundaries, nor of sex, for it is only in passing 

 that we need notice that one of the English 

 essayists is a woman. 



Among characteristics of these essays and 

 addresses as a whole, we may note the broad 

 tolerance and friendly tone shown by all the 

 writers, without exception. All recognize the 

 intellectual supremacy of Darwin, although 

 most of them have made some addition, large 

 or small, to the mass of fact and theory gath- 

 ered by the master. Each one is gently in- 

 sistent on his ovtm point of view. We may 

 compare Darwin to an explorer of a great 

 region, to whom fell the making of the first 

 map. While in many ways details have been 

 added to this map, not much of the original 

 scheme has been altered or taken away. While 

 many shrill voices from time to time have 

 been raised in criticism of one feature or 

 another of "Darwinism," yet the common 

 sense of the body of biologists has steadily 

 maintained the integrity of the original chart. 

 Natural selection very likely is not " all- 

 machtig." Darwin never claimed that it 

 was. But it is potent for all that, and the 

 other factors in evolution work with it, and 

 not in place of it. The scheme of the evolu- 

 tion of species, through variation and heredity 

 on the one hand, and the selective influence of 

 the environment on the other, has not greatly 

 changed since the date of the " Origin of 

 Species." The method, degree and to some 

 extent the causes of variation, have been crit- 

 ically and successfully studied. The meaning 

 and the machinery of heredity have been the 

 subject of most fruitful investigation and ex- 

 periment. Natural selection has been sub- 

 jected to the most searching analysis, and the 

 fact that its effects vary under varying condi- 

 tions has been clearly brought out. But it 

 still remains the only general cause of the 

 universal phenomena of adaptation of life to 

 environment. Isolation has been separated 

 from selection as a factor theoretically dis- 

 tinct, but practically coexistent. The sup- 

 posed Lamarckian factors have disappeared, to 



reappear again in unknown and perhaps un- 

 knowable forms. Theories of elemental spe- 

 cies, unit characters and the like, have arisen 

 to meet the facts and guesses involved in the 

 investigations of mutation and the rediscovery 

 of Mendelism, taking their place alongside of 

 Darwin's bold hypothesis of pangenesis, and, 

 like pangenesis, to pass away when the hy- 

 potheses are no longer needed. With aU this, 

 on the whole, the scheme of organic evolution, 

 as presented in the " Origin of Species," still 

 holds as an outline. The work of fifty years 

 has intensified the main features of the sketch, 

 and has constantly added to the work of the 

 master, without obliteration of any essential 

 details. 



The instruments of precision in biological 

 research have taught us many things. They 

 have shown a physical basis of heredity, and 

 by this means have made a theory of heredity 

 possible. Scientific experiment has added 

 many details, as to the development of cells, 

 as to the behavior of hybrids, as to the proc- 

 esses of selection, as to the effects, direct and 

 indirect, of many sorts of environments. Em- 

 bryology has shown the method of development 

 of each type of animal and plant. Our knowl- 

 edge of extinct forms has grown by leaps and 

 bounds. Even the lower ancestors of man 

 have appeared in the rocks and in the forms 

 the great morphologists have expected them to 

 assume. Systematic geologists have gathered 

 together the lessons of morphology, embryology 

 and paleontology, to be applied to the con- 

 struction of ancestral trees, while our knowl- 

 edge of geographical zoology and botany has 

 kept pace with the most rapid increase of 

 knowledge in any other field. With all this, 

 the entire face of philosophy, social science 

 and even of theology, has been altered by the 

 idea of descent, with modification, through 

 natural causes, the most noteworthy being that 

 of the survival of the fittest in the varied con- 

 ditions of life. 



In the American volume. Professor Thomas 

 C. Chamberlin contributes the introductory 

 chapter on the continuation of the Darwin 

 impetus, admitting, if necessary, that " if the 

 atom shall show an authenticated i)edigree," 

 it will " take its place in the procession of the 



