Page:George Archdall Reid 1896 The present evolution of man.djvu/145

Rh changes similar to the acquired changes in the parent.

This could only be determined by a further inquiry as to whether such clear and indubitable cases of reproduction by the offspring of the acquired variations of the parent, as the above, are common in nature. If it were found that they commonly occur, then the case for the transmission of acquired traits would be established beyond cavil, and we should have either to accept one of the current theories as to the way acquired variations are transmitted, or else to seek data whereon to found a theory which would present a greater appearance of probability than any of those yet formulated.

As a matter of fact, however, the phenomena of nature have already been ransacked for such clear cases of transmission, or apparent transmission, as the above, with the result that as regards the evolution of plants it is now admitted on all hands that the transmission of acquired variations can have played no part; as regards the higher animals alone is it generally claimed that such transmission has been important as a factor in evolution. Mr. Spencer says—

"See, then, how the case stands. Natural Selection, or survival of the fittest, is almost exclusively operative throughout the vegetal world, and throughout the lower animal world, characterized by relative passivity. But with the ascent to higher types of animals, its effects are in increasing degrees involved with those produced by inheritance of acquired characters; until, in animals of complex structures, inheritance of acquired characters becomes an important, if not the chief, cause of evolution" (p. 45).

With the first part of this statement we may well agree, but there are strong grounds for demurring to