DEVELOPMENT OF THE ORGANISM 



developed from an ordinary cat-fish? And if we admit this 

 must we not also admit that, here, at least, the young animal 

 recapitulates the past history of the race? 



In recent years the law of recapitulation has been proved 

 by experimental evidence. It 

 has been found that the black 

 and yellow salamander of 

 Europe (Salamandra macu- 

 losa) is capable of slowly 

 altering its colour as it grows 

 up; it makes its colour har- 

 monize with that of its sur- 

 roundings. If these young 

 salamanders are confined in 

 yellow boxes the yellow spots 

 on their skins enlarge in size 

 as they grow to maturity. If 

 they are confined in black 

 boxes the yellow spots 

 diminish in size and many of 

 them disappear. These 

 changes are in some degree 

 passed on to the offspring, for 

 if two "yellowed" sala- 

 manders are mated together 

 they produce young that are 

 much yellower than their 

 parents were at the corresponding stage of development, and 

 if these young continue to live amid yellow surroundings they 

 become almost entirely yellow when they are fully mature. 

 Now if the offspring of "yellowed" salamanders are reared 

 in black boxes they steadily become yellower for the first year 

 of their lives, thus recapitulating the experience through 



[53] 



Fig. 1. — Stages in the devel- 

 opment of the Indian cat-fish 

 Clar/us from an ordinary cat- 

 .iish. 



