EVIDENCE FROM EXPERIMENT 153 



water, the little creatures passed, in the course of 

 several generations, into quite a different form, 

 identical with what had previously been regarded as a 

 distinct species. On the other hand, by diminishing 

 the quantity of salt, and keeping many successive 

 generations in progressively freshened water, the 

 brine-shrimp gradually assumed the characters of 

 quite a distinct genus, which lives in fresh water. A 

 very important distinction between these results and 

 those obtained by Bouvier with plants, is that in the 

 latter case the change was effected immediately and 

 went no farther in succeeding generations, but could 

 be at once reversed by restoring the plant to its 

 original place of growth. With the brine-shrimps, on 

 the contrary, the changes were gradual and cumula- 

 tive, many generations being required to bring them 

 to full development. 



By keeping water-fleas in the dark, Kapterew 

 caused them to grow blind, the eyes losing their 

 regular outline, and their black pigment began to 

 wander over the head and body. At first this dete- 

 rioration appeared sporadically, but after a year and 

 a quarter all the individuals were similarly affected 

 and the blindness appeared to be hereditary. 



Many experiments have been made by Weismann, 

 Standfuss, Fischer, Schroder, Pictet and others upon 

 the caterpillars and cocoons of moths and butterflies, 

 changing their food-plants, in some cases, and in 

 others hatching the full-grown insects from cocoons 

 which had been exposed to abnormal conditions of 



