i.j BIOLOGY, PHYSICS AND CHEMISTRY 35 



to their own level by assimilating inorganic substances. 

 They construct the tissues. On the other hand, the actual 

 functioning of life (excepting, of course, assimilation, 

 growth, and reproduction) is of the katagenetic order, 

 exhibiting the fall, not the rise, of energy. It is only with 

 these facts of katagenetic order that physico-chemistry 

 deals — that is, in short, with the dead and not with the 

 living. 1 The other kind of facts certainly seem to defy 

 physico-chemical analysis, even if they are not anagenetic 

 in the proper sense of the word. As for the artificial 

 imitation of the outward appearance of protoplasm, should 

 a real theoretic importance be attached to this when the 

 question of the physical framework of protoplasm is not 

 yet settled? We are still further from compounding pro- 

 toplasm chemically. Finally, a physico-chemical ex- 

 planation of the motions of the amoeba, and a fortiori of 

 the behavior of the Infusoria, seems impossible to many 

 of those who have closely observed these rudimentary 

 organisms. Even in these humblest manifestations of 

 life they discover traces of an effective psychological activ- 

 ity. 2 But instructive above all is the fact that the ten- 

 dency to explain everything by physics and chemistry is 

 discouraged rather than strengthened by deep study of 

 histological phenomena. Such is the conclusion of the 

 truly admirable book which the histologist E. B. Wilson 



1 Cope, The Primary Factors of Organic Evolution, Chicago, 1896, pp. 

 475-484. 



1 Maupas, "Etude des infusoires cilies" (Arch, de zoologie experi- 

 mentale, 1883, pp. 47, 491, 518, 549, in particular). P. Vignon, Re- 

 cherches de cytologic generate sur les Epitheliums , Paris, 1902, p. 655. A 

 profound study of the motions of the Infusoria and a very penetrating 

 criticism of the idea of tropism have been made recently by Jennings 

 (Contributions to the Study of the Behavior of Lower Organisms, Wash- 

 ington, 1904). The "type of behavior" of these lower organisms, as 

 Jennings defines it (pp. 237-252), is unquestionably of the psychological 

 order. 



