442 ON THE TRIBES 



of the human mind towards the marvellous, that the 

 change of a caterpillar into a butterfly, when first noticed, 

 should have been considered by the ancients as a true 

 transformation irreconcileable with the ordinary course of 

 nature. Even on the mystery being in a great degree clear- 

 ed up by the discoveries of Libavius, Redi, Malpighi, and 

 Swammerdam, the phfenomenon continued to be termed 

 metamorphosis ; and perhaps it is even still a little owing 

 to such circumstances that a natural process, neglected in 

 other branches of Zoology, has always excited so much cu- 

 riosity among entomologists. Metamorphosis, however, has 

 been taken of late in a very general point of view, and ren- 

 dered synonymous with that species of organic decomposi- 

 tion which, by means of continual shedding of the external 

 envelopes, or even of the various integuments which may 

 compose these envelopes, occasions that extraordinary cha- 

 racteristic of a living body, namely, thatit never remains in a 

 constant state or identically the same, but is continually as- 

 similating new particles of matter as it throws off the old. 

 And since no metamorphosis can take place except in con- 

 sequence of these integuments being shed, perhaps it may 

 not be altogether improper to survey the subject in this light. 

 What I mean is, that we oughtto regard the metamorphosis 

 or change of form which certain animals undergo at various 

 periods of their life, as an attendant upon, if not a variety of, 

 the ecdysis or moulting, to which all organized beings are 

 subject. There is, however, a great distinction to be made 

 between iheecdy sis oii\\e Ferlebrata and Annulosa ; for in 

 the former we observe little more than that the animal has 

 quitted a sheath in which it was inclosed; whereas in the 

 latter, the change is nothing else than if the skeleton were 

 shed ; for this name is surely deserved by those hard and 



