October 6, 1911] 



SCIENCE 



419 



time, and is the pass-word of the younger 

 generation of biologists. 



Interwoven with this high aim which is 

 manifested in the biological work of recent 

 years is another tendency. It is the desire 

 to bring to bear upon our science, in greater 

 measure than before, the methods and re- 

 sults of the other sciences, both those that 

 in the hierarchy of knowledge are set above 

 and below, and those that rank alongside 

 of our own. 



Before the great problems of which I 

 have spoken, the cleft between zoology and 

 botany fades away, for the same problems 

 are common to the two sciences. When the 

 zoologist becomes a student not of the dead 

 but of the living, of the vital processes of 

 the cell rather than of the dry bones of the 

 body, he becomes once more a physiologist, 

 and the gulf between these two disciplines 

 disappears. When he becomes a physiolo- 

 gist, he becomes, ipso facto, a student of 

 chemistry and of physics. Even mathe- 

 matics has been pressed into the service of 

 the biologist, and the calculus of probabili- 

 ties is not the only branch of mathematics 

 to which he may usefully appeal. 



The physiologist has long had as his dis- 

 tinguishing characteristic, giving his craft 

 a rank superior to the sister branch of 

 morphology, the fact that in his great field 

 of work, and in all the routine of his ex- 

 perimental research, the methods of the 

 physicist and the chemist, the lessons of the 

 anatomist, and the experience of the physi- 

 cian are inextricably blended in one com- 

 mon central field of investigation and 

 thought. But it is much more recently 

 that the morphologist and embryologist 

 have made use of the method of experi- 

 ment, and of the aid of the physical and 

 chemical sciences — even of the teachings of 

 philosophy : all in order to probe into prop- 

 erties of the living organism that men were 

 wont to take for granted, or to regard as 



beyond their reach, under a narrower inter- 

 pretation of the business of the biologist. 

 Driesch and Loeb and Roux are three 

 among many men who have become emi- 

 nent in this way in recent years, and their 

 work we may take as typical of methods 

 and aims such as those of which I speak. 

 Driesch, both by careful experiment and by 

 philosophic insight, Loeb, by his conception 

 of the dynamics of the cell and by his mar- 

 vellous demonstrations of chemical and 

 mechanical fertilization, Roux, with his 

 theory of auto-determination, and by all 

 the labors of the school of Entwickelungs- 

 mechanik which he has founded, have all 

 in various ways, and from more or less 

 different points of view, helped to recon- 

 struct and readjust our ideas of the rela- 

 tions of embryological processes, and hence 

 of the phenomenon of life itself, on the one 

 hand to physical causes (whether external 

 to or latent in the mechanism of the eeU), 

 or on the other to the ancient conception of 

 a vital element alien to the province of the 

 physicist. 



No small number of theories or hypoth- 

 eses, that seemed for a time to have been 

 established on ground as firm as that on 

 which we tread, have been reopened in our 

 day. The adequacy of natural selection to 

 explain the whole of organic evolution has 

 been assailed on many sides ; the old funda- 

 mental subject of embryological debate be- 

 tween the evolutionists or preformationists 

 (of the school of Malpighi, Haller and 

 Bonnet) and the advocates of epigenesis 

 (the followers of Aristotle, of Harvey, of 

 Caspar F. Wolff and of Von Baer) is now 

 discussed again, in altered language, but as 

 a pressing question of the hour; the very 

 foundations of the cell-theory have been 

 scrutinized to decide, for instance, whether 

 the segmented ovum, or even the complete 

 organism, be a colony of quasi-independent 

 cells, or a living unit in which cell differ- 



