246 Causes and Course of Organic Evolution 



In reply it can be said that during the past half century 

 the physical necessity for division to occur in any steadily 

 gro^^ing colloid vesicle, if it is to preserve its vesicular char- 

 acter, has been fully recognized since Herbert Spencer first 

 drew attention to the physics of the act. 



Hartog (97: 23) has fully emphasized and illustrated the 

 case thus: '* Growth of an organism which retains its shape 

 alters the ratio of the surface area to the whole volume, so 

 necessary for the changes involved in life. For the volume 

 of an organism varies as the cube of any given diameter, whereas 

 the surface varies ^\-ith the square only. Without going into 

 the arithmetical details, we may say that the ratio of surface 

 to volume is lessened to roughly four-fifths of the original 

 ratio when the cell doubles its bulk. As Herbert Spencer and 

 others have pointed out, this must reduce the activities of the 

 cell, and the due ratio is restored by the division of the cell 

 into two. This accounts for what we must look on as the 

 most primitive mode of reproduction, as it is the simplest, 

 and which we term "fission" at Spencer's "limit of growth." 

 In a footnote the above named writer then works out some 

 exact examples aritlimetically wliich demonstrate the correct- 

 ness of these views. 



Now the multiplication here, that is coextensive with for- 

 mation of new individuals, is a process that probably wholly 

 is due to osmotic relation of the cells and of their contents, 

 to the liquids by which they are surrounded. Thus Leduc 

 describes (23: 124) the artificial formation of colloid vesicles 

 through the dropping of "a fragment of fused calcium chloride 

 into a saturated solution of potassium carbonate or tribasic 

 potassium phosphate." As a result a vesicle or cell is formed 

 by the calcium chloride. Then "the first cell gives birth to 

 a second cell or vesicle, and this to a third, and so on, so that 

 we finally obtain an association of microscopic cellular cavities, 

 separated by osmotic walls — a structure completely analogous 

 to that which we meet with in a living organism. . . . The 

 membranogenous substance, the chloride of calcium, diffuses 

 uniformly on all sides from the solid nucleus, and forms an 



