. Adventures with animals and plants. Biology. PROBLEM 4. The Effect of the Environment on the Organ'mn 489. A B C D Fig. 438 The cats shoivii are fe/nale cats. A sperm cell is shown about to fertilize the egg (a^); other sperms fertilize the eggs of succeeding generations. What is the shaded substance in each individual? Where is the somatoplasm? The egg (a^) and the sperm cell can be spoken of as germ plasm. The resulting fertilized egg for?ns more germ plasm like itself ajid it also for?fis so7fiatoplas7/7, the body of cat (B). You can see that cat (B) did not produce its germ plasm. It onl
. Adventures with animals and plants. Biology. PROBLEM 4. The Effect of the Environment on the Organ'mn 489. A B C D Fig. 438 The cats shoivii are fe/nale cats. A sperm cell is shown about to fertilize the egg (a^); other sperms fertilize the eggs of succeeding generations. What is the shaded substance in each individual? Where is the somatoplasm? The egg (a^) and the sperm cell can be spoken of as germ plasm. The resulting fertilized egg for?ns more germ plasm like itself ajid it also for?fis so7fiatoplas7/7, the body of cat (B). You can see that cat (B) did not produce its germ plasm. It only carries the germ plasm which is a continuatioit of the germ plasm of cat (A) plus the sperm. Can the body affect the germ plasm? Remember that the germ plasm (pri- mary sex cells) is held within the body or soma; it is not produced by the soma. Therefore Weismann argued that, even though the soma may become changed, even though it may acquire new charac- teristics during the lifetime of the animal or plant, these acquired characteristics are not passed on to the germ plasm or priman^ sex cells. This was a reasonable conclusion for Weismann to arrive at. And nowadays we still accept it as true. In fact, since we have learned about mi- tosis and genes we have all the more rea- son for believing that acquired charac- ters are not passed on to the new organ- ism. Even in those lower animals and plants which do not have distinct soma- toplasm and germ plasm there is every reason to believe that the genes are not changed even though environmental changes may occur in the cells. Weismann arrived at his conclusion as the result of a famous experiment in which he cut off the tails of white mice for almost twent)^ generations. As each generation grew to maturity he measured the tails of the mice before cutting them off. He found that the tails neither dis- appeared nor grew shorter. From this he concluded that the environment changes the body but that the germ cells are not affected by
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