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?
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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 maculosa) is capable of slowly altering its colour as it grows up; it makes its colour harmonize with that of its surroundings. 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” salamanders 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
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