VII 

 EXPERIMENTS ON CLEAVAGE 1 



1. IN the second part of my Untersuchungen zur physio- 

 log ischen Morphologic 2 I showed that regeneration and 

 growth in animals are, as in plants, a function of the amount of 

 water contained in the cells. When I increased the amount of 

 water in the cells of Hydroids by bringing these organisms 

 into more diluted sea- water than that in which they usually 

 live, the rate of growth increased with the decrease of the con- 

 centration of the sea-water. When I diminished the amount 

 of water in the tissues of Hydroids by bringing these animals 

 into a more concentrated solution than the normal sea-water, 

 the rate of growth diminished too. We know that seedlings 

 of plants need water in order to develop. It is the same in 

 the animal egg, as recent investigations concerning the 

 development of sea-urchins, starfish, arthropods, and fish 

 showed me. If we reduce the amount of water contained in 

 the egg of the sea-urchin by bringing it into more concen- 

 trated sea- water, the process of segmentation is retarded 

 only as long as the increase in the concentration is small. 

 As soon as the concentration is greater, however, the fertil- 

 ized egg does not segment at all. In one case the eggs had 

 been fertilized at 9 : 40 A. M. A few minutes after the impreg- 

 nation, one part (a) of the eggs were put into sea-water to 

 which 1 g. of NaCl to 100 c.c. had been added. A second 

 part (&) were put into sea- water to which I had added 1.3 g. 

 of NaCl to 100 c.c. A third part (c) were brought into sea- 

 water, the concentration of which was increased by the addi- 

 tion of 2 g. of NaCl to 100 c.c. ; and a fourth part (d) 



i Journal of Morphology, Vol. VH (1892), p. 253. 

 SWarzburg, 1892. Part I, p. 191. 



253 



