Modification of Development 171 



individual. In other cases, however, the modification seems 

 to bear no relation to the welfare of the organism. 



Modification of Development 



Many of the influences of environment are familiar 

 enough since they leave the individuals, however they may 

 differ from the " type," still within the boundaries of our 



^^< A 



Fig. 44. Relation of Salt to Development 



The experiments of Schmankewitsch have been repeated by others. 

 The brine-shrimp Artemia arietina, C, lives in brackish water. By dilut- 

 ing the water slowly modifications are brought about in the appearance of the ani- 

 mal, so that in a few generations it seems to be a totally different animal — B, A; 

 by concentrating the water modifications are brought about in an opposite direc- 

 tion — D, E. A and B have been known as species of Branchipus. The changes 

 can be reversed, and include diflferences in the proportions of the body and tail 

 (abdomen), the degree of branching and numbers of bristles on the tail, the size of 

 the head organs, and the mode of reproduction. After Abonyi. 



conception of species. When an excess of iron in the soil 

 makes the hydrangea bear bluish flowers instead of the usual 

 white blossoms, the divergence does not raise the question of 

 new species. Diluting sea water with fresh water, Schmanke- 

 witsch was able to influence the development of certain water 

 fleas, so that they took on the appearance of what had been 

 considered a totally different species; and he was able to re- 

 verse the process by increasing the concentration of the 

 brackish water (Fig. 44) . 



