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cal forces that make a tree bear fruits are put into operation by the tree.
(5) Niyati or accidental element. Events sometimes occur all unexpected i. e. without any assignable causes. A prominent instance of this even in the scientific sphere is the curious result obtained by De Vries in his famous experiments on some trees. Evolution in the organic world is supposed to be continuous; it always proceeds by small variations-nature preserving the varia. tions that are useful and transmitting them to offsprings. In some of his experiments, however, notably on some trees De Vries found that large variations were suddenly emergent in the progeny without any assignable causes whatsoever. This has led many biologists to doubt the tenability of the current view that organic evolu tion is uniformly continuous. From many other observations and similar experiments, De Vries came to the conclusion that evolution is often discontinuous, which is another way of saying that sometimes accidental and unknown factors intervene in the emergence of a phenomenon.
It would be seen that of the above factors in the modifications of an object, the first and the last are external and the rest, internal. The five factors or elements do not operate, each indepen
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