In order, then, to have some name for these remarkable phenomena, and to distinguish them from those cases in which the _mature_ animal or plant is represented by two or more different forms, I think it would be convenient to retain exclusively for these latter the terms dimorphism and polymorphism; and those cases in which animals or plants pass through a succession of different forms might be distinguished by the name of dieidism or polyeidism. The conclusions, then, which I think we may draw from the preceding considerations, are:— 1. That the occurrence of metamorphoses arises from the immaturity of the condition in which some animals quit the egg. 2. That the form of the insect larva depends in great measure on the conditions in which it lives. The external forces acting upon it are different from those which affect the mature form; and thus changes are produced in the young, having reference to its immediate wants, rather than to its final form. 3. That metamorphoses may therefore be divided into two kinds, developmental and adaptional or adaptive. 4. That the apparent abruptness of the changes which insects undergo, arises in great measure from the hardness of their skin, which admits of no gradual alteration of form, and which is itself necessary in order to afford sufficient support to the muscles. 5. The immobility of the pupa or chrysalis depends on the rapidity of the changes going on in it. 6. Although the majority of insects go through three well-marked stages after leaving the egg, still a large number arrive at maturity through a greater or smaller number of slight changes. 7. When the external organs arrive at this final form before the organs of reproduction are matured, these changes are known as metamorphoses; when, on the contrary, the organs of reproduction are functionally perfect before the external organs, or when the creature has the power of budding, then the phenomenon is known as alternation of generations. CHAPTER V. _ON THE ORIGIN OF INSECTS._ “Personne,” says Carl Vogt, “en Europe au moins, n’ose plus soutenir la Création indépendante et de toutes pièces des espèces,” and though this statement is perhaps not strictly correct, still it is no doubt true, that the Doctrine of Evolution, in some form or other, is accepted by most, if not by all, the greatest naturalists of Europe. Yet it is surprising how much, in spite of all that has been written, Mr. Darwin’s views are still misunderstood. Thus Browning, in one of his recent poems, says:— “That mass man sprang from was a jelly lump Once on a time; he kept an after course Through fish and insect, reptile, bird, and beast, Till he attained to be an ape at last, Or last but one.”[53]