June 7, 1895.] 



SCIENCE. 



623 



coustaut an accompauimeut of development 

 that the forces of the hatter may be divided 

 into the kinetogenetic. or those that develop 

 movement, and the statogenetic, or those 

 that develop rest or equilibria, amongst the 

 parts of the germ. The kinetogenetic forces 

 ai"e the consequences of metabolism, but 

 the statogenetic forces, though dependent 

 upon metabolism, are produced as a conse- 

 quence rather of the interaction of the sur- 

 face layers of the plasma of the cells, con- 

 templated as if they were small cohering 

 masses of viscous dead matter. These 

 masses are separated, iu the organism or 

 germ, bj' interfacial planes, free and inter- 

 facial curved surfaces that are the results 

 of segmentation and growth, and the extent 

 of the areas of which obey a law first pointed 

 out in relation to soap-bubbles by the Ijlind 

 physicist Plateau, who showed that such 

 bubbles tended to form interfacial films and 

 surfaces, wherever in contact with each 

 other, of an area that was the minimal con- 

 sistent with their statical equilibrium. =^ In 

 this connection it may also be remarked 

 that, inasmuch as the cells of a germ or or- 

 ganism are always iu statical equilibrium, 

 their surface layers of molecules also always 

 represent complex systems of equipotential 

 surfaces, no matter how intricate the form 

 of the organism may be. Since the equi- 

 libria between the molecules of the surface 

 layers of cells can normally be disturbed 

 only by the metabolism incident to physio- 

 logical activity, it is evident that the figure 

 of the organism must ultimately be ascribed 

 to the action of metabolism or to the func- 

 tions of the organism as affecting the phys- 

 ical properties of its plasma. 



A statical e<iuilibrium in a living cell 

 may be one in which it is not in contact 

 with others at any point on its surface, as 



* Some interesting applications of the geometrical 

 theory of radical axes and centere also apply here 

 that have never been studied in connection ^vith the 

 phenomena of scjjmentiitiou. 



in the case of blood-corpuscles or disks. 

 Or a cell may be greatly extended in one 

 direction, as in the case of the axis-cylinder 

 of a nerve-cell, owing to very unequal sur- 

 face-tensions developed in one or more di- 

 rections so as to draw it out into a condi- 

 tion of equilibrium, iu assuming which it 

 acciuires a great length. Formal changes iu 

 cells, no matter how irregular these may 

 become, must be due to alterations of sur- 

 face-tension due to molecular transforma- 

 tions at certain points on the surface df 

 globular or polyhedral em)>ryonic cells. 

 The final mature form of a cell is a conse- 

 quence of the assumption of a statical equi- 

 librium amongst its parts, due to the nature 

 of its metabolism and its consequent molecu- 

 lar structure. The statogenetic factors of 

 development are therefore of just as much 

 importance as the kinetogenetic, or those 

 involving motion. The statical forces that 

 are developed in individual cells also act 

 reciprocally between all of the cells of the 

 organism, so that in this way the efiect of 

 statogeny extends throughout the entire 

 organism. 



If there were no such statical forces to be 

 overridden by the purely kinetic ones de- 

 veloped by the molecular transformations 

 and consequent motions incident to metab- 

 olism, provided the latter, together with 

 assimilation, took place, during develop- 

 ment, with great rapidity, the ontogeny of 

 an organism would take place with such 

 swiftness that it could not be successfully 

 studied by embrj'ologists. In other words, 

 ontogeny would take place in the twinkling 

 of an ej'e, and organisms as large as whales 

 might even mature in an instant, provided 

 the coeflicieuts of viscosity and surface-ten- 

 sion of their plasma were to fall nearly to 

 zero, while assimilation and metabolism 

 proceeded with infinite rapidity. 



It follows also from what has preceded 

 that we can now form some idea why ap- 

 parent rejuvenescence occurs in every on- 



