154 METAMORPHOSIS 



place only late in life and after growth has been completed. Insects 

 leave the egg in a certain form, and in that condition they con- 

 tinue with, however, a greater or less amount of change according 

 to kind till growth is completed, when, in many cases, a very great 

 change of form takes place. Post-embryonic development, or 

 change of form of this kind, is called metamorphosis. It is not a 

 phenomenon peculiar to Insects, but exists to a greater or less 

 extent in other groups of the Metazoa ; while simpler post- 

 embryonic development occurs in nearly all, as in scarcely any 

 complex animals are all the organs completely formed at the time 

 the individual becomes possessed of a separate existence. In 

 many animals other than Insects the post-embryonic development 

 assumes most remarkable and complex forms, though there are 

 perhaps none in which the phenomenon is very similar to the 

 metamorphosis of Insects. The essential features of metamor- 

 phosis, as exhibited in the great class we are writing of, appear 

 to be the separation in time of growth and development, and the 

 limitation of the reproductive processes to a short period at the 

 end of the individual life. The peculiar phenomena of the post- 

 embryonic development of the white ants show that there exists 

 some remarkable correlation between the condition of the repro- 

 ductive organs and the development of the other parts of the 

 organisation. If we take it that the post -embryonic physio- 

 logical processes of any individual Insect are of three kinds, 

 growth, development, and reproduction, then we may say 

 that in the higher Insects these three processes are almost 

 completely separated, and go on consecutively, the order being, 

 first, growth ; second, development ; third, reproduction. While, 

 if we complete the view by including the processes comprised in 

 the formation of the egg and the development therein, the series 

 will be (1) oogenesis, or egg-growth; (2) development (embry- 

 onic) ; (3) growth (post -embryonic) ; (4) development (post- 

 embryonic) ; (5) reproduction. 



The metamorphosis of Insects is one of the most interesting 

 parts of entomology. It is, however, as yet very little known 

 from a scientific point of view, although the simpler of its 

 external characters have for many ages past attracted the 

 attention and elicited the admiration of lovers of nature. It 

 may seem incorrect to say that little is yet known scientifically 

 of a phenomenon concerning which references almost innumer- 



