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15 of conditions of temperature and light under which the caterpillars and pupae are reared. Again changes are often seen in the colour of birds, caused by feeding them on different foods. J.T.Cunninghame in the 1893 has shown the changes in colour produced in flat fish when exposed to the light. An account of H.W. Vernon's work on Echinoderms 13 given in 1897. The sizes of the larvae and the proportion of their different parts may be altered by mere changes of temperature. Changes are also produced by altering the salinity of the water or the proportion of nourishing substances contained in it.

Again there is the well-known case of, where we have one species of this phyllopod crustacean changed into another, by altering the amount of salt in the water.

Thus a mass of evidence is growing which shows how variations in the structures and the forum of animals and especially of plants may arise as a result of environmental changes.

Now many of the characters which are thus changed have hitherto been regarded as specific characters. This at once raises the question of whether or not all Specific characters are congenital. If they are all inborn then it must follow that the characters due to environmental changes are transmissible by inheritance. If on the other hand the specific characters in question are not inherited they must be acquired afresh by each generation. On this view acquired characters would play