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14 in the belief that by altering the conditions of temperature, light, moisture and especially nutrition, under which the plant is growing, many of its characters will become modified permanently. De Vries, for instance, in the account which he gives of his cultivation of monstrosities shows this to be the case. Taking the poppy as an instance he shows it entirely depends upon the manuring, upon the distance left between the seedlings, upon the temperature and light supplied, etc., - whether he obtains from the seeds of the many-headed variety of poppy similar forms or individuals which will only have the rudiments of the additional heads. He points out that influences must be brought to bear on the plant in early youth, otherwise the results are not shown. The keeping up of the new variety, also, depends upon its nutrition. Botanists also lean to the belief that these acquired characters are transmitted by inheritance.

Among animals the evidence is not so clear. But many interesting observations have been recorded. A seasonal dimorphism is often seen in moths and butterflies. Experiments conducted by Mfield, Weismann, Standfs and others, have proved that "one or the two forms may be bred from larvae of the other form by simply altering the temperature under which the larvae are reared".

Poulton in his book on gives an account of the changes or colour in butterflies caused by the differences