5| THE POPULAR SCIENCE MONTHLY. 



lived, increased in volume, and multiplied by division, because 

 the vital exchanges could, not be efficacious and properly regu- 

 lated except on condition that the mass bore a well-determined 

 proportion to the surface. If the mass became too great, the 

 surface would become insufficient, the mass increasing in propor- 

 tion to the cube of the radius, and the surface in proportion only 

 to the square of the same radius. 



The little protoplasmic masses created under special conditions 

 of the medium would continue in that medium as long as it re- 

 mained the same. But this medium becomes modified, because 

 it ceases to be what it was — a fact clearly established by geology 

 and paleontology — and we may presume that the modifications 

 were made slowly and progressively. The little protoplasmic 

 masses would also modify themselves and adapt themselves to 

 the conditions created around them. The medium being changed, 

 the living being would be changed too ; but, the medium changed, 

 the conditions that had permitted the direct formation of living 

 matter, spontaneous or heterogeneous variation, would also have 

 vanished. The new medium would then be such that the little 

 living masses already created would continue to live, adapting 

 themselves to it, but that new living masses could not be directly 

 formed in it. 



The first little masses born on the whole surface of the globe, 

 unless the conditions were much more uniform than they are 

 now, became the starting-point of successive generations, which, 

 obeying the law of progress that presides over evolution and sub- 

 jected to the conditions of the medium, acquired successively 

 differentiations, very slow, but progressive, which determined in 

 the homogeneous mass the appearance of granulations, localiza- 

 tions, limited condensations, partitionings, networks, etc., that 

 made of the homogeneous droplet a more or less complicated 

 organism. Such were the very slow advances, not becoming per- 

 ceptible till after very long periods and through millions of suc- 

 cessive generations. The nucleus of the cell, the muscular fiber, 

 the nervous cell, the grain of starch, the fatty globule, the secre- 

 tory cell, etc., were not formed by Nature at the first stroke. They 

 are probably the result of work performed during millions of 

 years and through milliards of generations. These milliards of 

 generations of living droplets or living cells have therefore been 

 as many little laboratories, in each of which has been elaborated, 

 perfected, and differentiated the muscular fiber or grain of 

 starch. Each of these little laboratories has brought to this 

 work some share of activity, and each has added something to 

 the differentiation. > 



Some, for example, have begun by producing more specially 

 contractile particles in the homogeneous protoplasm ; others have 



