444 ON THE TRIBES 



necessarily confounded. It is also visible in reptiles and spi- 

 ders, where such appendages of the trunk as have been lost 

 may be reproduced by continued moulting. When the 

 various envelopes are all cast as it were in one mould, it 

 is to be expected that the proper form of the animal should 

 reappear as these continue to be thrown off. The return 

 therefore of a spider or crab, after having lost a limb, to its 

 original form, may be in some measure understood as de- 

 pending on the manner in which such animals shed their en- 

 velope ; but that the limbs thus shot forth should be furnish- 

 ed with muscles and nerves, is, I conceive, what cannot be 

 accounted for, except by referring to that polype nature of 

 the cellular substance which is perhaps, in the opinion of 

 some persons, the foundation of all ecdysis. If perfect Hex- 

 apod insects cannot reproduce their members, this inability 

 may probably proceed from a cause which appears to have 

 produced the same effect among Mammalia and Birds, to 

 wit, that these animals in their perfect and final form are all 

 subject, if to any, at least to a very imperfect ecdysis. 



The second sort of complete ecdysis is that where the 

 under envelope has been cast in a somewhat different mould 

 from the upper ; so that in the course of the moulting cer- 

 tain new parts become gradually developed without the 

 general form being in any material degree altered. This is 

 observable in every Annulose class, as well as in Humboldt's 

 Axotl among the I'ertebrata, and is the first species of 

 change which merits the name of Metamorphosis. It in- 

 cludes the Metamorphosis inchoala and Metamorphosis di- 

 midiaia of Latreille, and is the same with the Mttamorphose 

 partielle of Lamarck. 



The third sort of complete ecdysis is that wherein by 

 some two or three moultings, generally the last which the 



