THE EVIDENCE FROM THE LIFE-HISTORIES OF INSECTS. 255 



into the giant quadruped which takes its leap of twenty feet with the 

 utmost ease. So, also, we find in the development of birds well- 

 nigh infinite variety in the stage of perfection at which the young 

 animal is thrown upon its own resources. Of old, naturalists were 

 wont to divide the birds into those which could run about and forage 

 for themselves immediately on leaving the egg, and those which, as 

 mere fledglings, required parental care and attention for a longer or 

 shorter period after bursting the shell. A young chicken is a much 

 more independent being than, say, an infant thrush ; and numerous 

 other comparisons might similarly be instituted, with a like result of 

 showing variations in the development of even the animals of a 

 single class. 



It seems, therefore, correct to say that the term " metamorphosis " 

 is one of very considerable latitude, and one admitting, in fact, of 

 no rigid definition at all. At the best its value is merely relative, and 

 those animals may be regarded as really most " metamorphic," so to 

 speak, which leave the egg in an immature state, and which, through 

 circumstances which it is our business to trace in this chapter, have 

 to pass through a definite or well-marked set of changes in form, 

 shape, and often of size also, before assuming the likeness of the 

 parental form. If we reflect that every living being springs from a 

 mere speck of protoplasm, devoid of all structure, which we 

 call "germ" or "egg," and which contains the potentialities of 

 becoming what its parent now is ; or if we further consider that 

 from this speck of albumen there is developed in a few days, as in 

 the case of the chicken, a creature rejoicing in the possession of a 

 complex system of bone, muscle, sinew, brain, nerve, and sense 

 organs we may well feel inclined to consider such a transformation 

 and development as thorough an example of " metamorphosis " as, and 

 as a far higher development than, that of the insect which attracts 

 our notice simply because it is more evident to our eyes. Another 

 striking proof that " metamorphosis " must be, after all, a comparative 

 term, lies in a knowledge of the fact insisted on and illustrated in a 

 previous chapter namely, that the eggs of all animals, from sponge to 

 man, pass through the same stages up to and including a given point, 

 at which each group branches off, so to speak, on its own pathway 

 towards adult and specific perfection. Thus, why one animal under- 

 goes those changes of form we see in the insect, and why another 

 does not, are circumstances to come to details depending, firstly, on 

 the size of the egg from which it is developed, and concurrently on 

 the amount of nourishment the egg contains ; and, secondly, upon 

 the varying circumstances and surroundings of its life, as well as 

 on the life and history of its race, as temporarily represented by its 

 parent. Thus a large-sized egg, with a big yolk, will, cateris 

 paribus, produce an animal in a higher and more perfect stage of 



