624 



SCIENCE. 



[N. S. Vol. I. No. 23. 



togeny. Every germ must, for assignable 

 reasons, begin its existence in the original, 

 highly complex, feolotropic condition of the 

 plasma of its species. It must therefore 

 begin its career somewhat in the guise of 

 the mechanically unspecialized plasma of a 

 remote unicellular ancestor. Unlike that 

 ancestor, however, the cells that result from 

 its growth and segmentation cohere until a 

 multicellular aggregate results, the different 

 regions of which fall into certain statical 

 sISites in relation to one another and to the 

 earth's centre, in virtue of the action of the 

 forces of cohesion, friction, gravitation, etc. 

 The diiferent regions of such an aggregate 

 now adjust themselves to the surroundings 

 in such a way that nearly constant eifects 

 of light, heat, etc., begin to control or afiPect 

 the functions of such an aggregate dynamic- 

 ally through its metabolism. Function, 

 thus conditioned, asserts itself under the 

 stress of mechanical adaptation or adjust- 

 ment that becomes increasingly complex with 

 every advance in ontogeny. Every step in 

 ontogeny becomes mechanically adaptive 

 and determinative of the next. It is thus 

 only that we can understand the wonderful 

 molecular sorting process that goes on in 

 ontogeny, for which others have invoked 

 infinite multitudes of needless ' gemmules,' 

 ' biophors ' and ' determinants.' 



It is the whole organism that develops in 

 continuity or coordination ; not its nuclei, 

 centrosomes, and asters only. The whole 

 organism, molecularly considered, is as 

 fixed and immutable, within variable limits, 

 as a crystal. Its development, moreover, 

 becomes intelligible only if we contemplate 

 its ontogeny somewhat as we would the 

 growth of a crystal, with the additional 

 supposition that its growth is not condi- 

 tioned by forces operating along straight 

 lines having a constant angular divergence 

 as in the latter. On the contrary, living mat- 

 ter is capable of developing curved bound- 

 ing surfaces in consequence of the perma- 



nently mobile nature and cohesion of its 

 molecules, that, as a complex djniamical 

 mechanism, can operate so as to tell off the 

 tale of its ti-ansformation in but one way, in 

 consequence of the order and waj' in which 

 the energy of its constituent molecules is 

 set free during ontogeny. Upon the com- 

 pletion of ontogenj' a phrase is reached in 

 which the income and outgo of metabolism 

 is in equilibrium. The duration of life de- 

 pends upon the length of time that this 

 equilibrium can be maintained without fatal 

 impairment of the harmonious operation of 

 its mechanism under the stress of the dy- 

 namical conditions of life. This may be 

 considered the cause of death, so that the 

 length of the life of the indi^'idual is deter- 

 mined by the possible number of harmo- 

 nious molecular transformations of which its 

 plasma is capable as a mechanism. 



The doctrine that cells undergo differen- 

 tiation in relation to other adjacent cells, or 

 that the destiny of a cell is a function of its 

 position (Driesch), is no doubt true. Nev- 

 ertheless, we have in organisms machines of 

 such complexity, dynamical potentialitj', 

 and power of transformation, that in com- 

 parison a study of the theories of crystal- 

 lography is simplicity itself. In organisms 

 we have the polarities of head and tail, 

 stem and root, right, left, dorsal and ven- 

 tral aspects, as definitely marked out as 

 are the relations of the axes of crj^stals. In 

 the organism we have diffuse, intussuscep- 

 tional growth in three dimensions, by means 

 of the osmotic interpolation of new mole- 

 cules, whereas, in the crystal, growth is 

 superficial, but consequently also tri-dimen- 

 sional. In the organism the molecules are 

 mobile within limits ; in the crj^stal thej'^ are 

 fixed. ISTevertheless, we may justlj' regard 

 organisms as developing after the manner 

 of crystals, but with the power of very 

 gradually varjung their forms by means of 

 variation in the structure, forms and pow- 

 ers of their constituent molecules, in the 



