CELLULAR ORGAXIZA TlOX OF LULXG MA'ITKR .i 



from unrestricted dilYusive iiUerchan^f.' Ii i.^ t-\uiLiiL 

 that if a minute portion of pr()t()i)lasm is to retain its 

 special chemical organization, il must he protected 

 against loss of its water-soluhle constituents hy dilYusion, 

 and also against the unregulated entrance of soluble 

 substances from without. Chemical analysis shows 

 in fact that the crystalloidal content of living cells is 

 ty})ically widely different from that of the surrounchng 

 medium.'' The presence of a (HlYusion-proof partition 

 separating each small portion of living j^rotoi^lasm from 

 its surroundings is apparently an essential feature of the 

 cellular organization. 



Without such a diffusion-hindering type of structure, 

 it is difficult to see how a high degree of chemical differ- 

 entiation could be maintained in such a system as the 

 living organism, consisting, as it does, in large part of 

 an aqueous solution of diffusible substances. Ditlerences 

 in the distribution of soluble substances between i)roto- 

 plasm and surroundings would tend to ecjualize them- 

 selves by diffusion, and chemical differentiation would 

 become difficult or impossible. Alor])hological dilTer- 

 entiation has long been recognized as favored by the 

 subdivision of the developing germ into cells; this 

 condition permits moq^hogenetic i)rocesses in neighboring 

 cells and cell groups to proceed in relative indei)en(lence 

 of one another.^ In a similar manner an essential 



* Cf. my paper in Biological Bulletin, XVII (iQog), iSS, for a fuller 

 discussion. 



* For a summary of work in this field, cf. liulx-rs I' "-c 

 Chemie dcr Zelle und dcr Gcwcbe (1914), pp. 370. 4U>; tf. also iioiu-^is 

 article in Winlersteins Handhuch dcr vcrgl. Physiol., I (191 1), 37. 



3 Cf. F. R. Lillic, "Adaptation in ClcavaKc," Woods Hole Btoi< 

 Lectures (1899), p. 43. 



