82 THE MECHANISM OF LIFE 



pletelv absorbed the six smaller ones, and only one large drop 

 will remain. 



Incubation. — In the living organism we frequently find 

 conditions similar to those realized in this experiment, viz. 

 very slow movements of diffusion in liquids containing particles 

 in suspension. In such cases the consequences must be the 

 same, viz. granulation and segmentation. Consider for a 

 moment the incubation of an egg. The heat of incubation 

 determines a certain amount of evaporation through the 

 shell, with a concentration of the liquid near the surface. As 

 a consequence of this superficial concentration we get 

 segmentation of the vitellus, with the production of a morula. 



Artificial Parthenogenesis. — The experimental partheno- 

 genesis of Loeb and Delage consists in plunging the e^s into 

 a liquid other than sea water, and returning it again to its 

 original medium. This operation will necessarily determine 

 slow movements of diffusion in the egg, which will give rise 

 to segmentation. It may be objected that segmentation is 

 also produced by a solution which is isotonic with sea water. 

 Such a solution would not indeed produce an exchange of 

 water with the egg, but it would set up an exchange of 

 electrolytes, since there would be a difference of their osmotic 

 pressure in the egg and in the new isotonic medium. The 

 extremelv slow movements of diffusion thus produced would 

 be very favourable to the action of the cohesive force on 

 the particles in suspension, and hence to the segmentation 

 of the egg. 



Few physical phenomena give us a deeper insight into the 

 phenomena of life than those which we here contemplate. 

 There is still another experiment which is even more convinc- 

 ing. On the surface of our horizontal salt solution we sow 

 a number of drops of a more concentrated salt solution 

 at equal distances around the circumference of a circle. 

 Movements of diffusion are thus set up in the interior of 

 the circle, and alter a time, when this diffusion has become 

 so slow as to be almost imperceptible, a furrow begins to 

 appear in the coloured mas<. Then a second and third 

 appear, and others crossing the former break up the mass 



