THE METAMORPHOSIS. 429 



also many auxiliary ones, were divested of their tunic, and likewise the 

 internal tunic of the colon remained attached to the peeled case. We 

 have likewise above drawn attention to the uniformity of the external 

 epidermis with the mucous tunic of the internal organs, and by a 

 similar pathological phenomenon, shown their affinity. Thus, the 

 observations of equally credible witnesses and the several theories clash 

 together. It is difficult to discover the truth in the midst of such con- 

 tradictions. To conclude that in one order such a changing of the 

 skin exists, but not in the other, appears inadmissible, as nature in 

 general pursues in its process of development a certain uniformity. 

 Perhaps, however, we may find an outlet if we adopt that in smaller 

 individuals the internal tunic of the intestinal canal is more easily 

 absorbed, whereas in the larger ones, furnished with a coarser mucous 

 membrane, it is rejected. Many observations speak in favour of such an 

 absorption, namely, the absorption of the mucous membrane of the egg- 

 tube at its lower extremity, where it stands in connexion with the 

 oviduct after it has developed the lowest egg at this spot, and then has 

 passed into the oviduct itself ( 210). But the perfect explanation 

 and determination of this doubt remains still as the problem of careful, 

 prolonged, and comprehensive experiments and observations. 



254. 



The number of moultings of the larva until its full growth appears to 

 vary considerably in different families and genera. " It may be 

 assumed in general that they change their skin three times. This is 

 the case in all insects with an incomplete metamorphosis. After the 

 first change the larva has merely increased in size, but during this 

 second period of its existence the rudiments of the wings form beneath 

 the skin ; consequently, after the second moulting, these incipient wings 

 present themselves externally as small leaves, which cover the sides of 

 the first abdominal segment ; these larvae are called nymphs *," it 

 being analogous to the pupa state of other insects. When this pupa 

 again moults the insect attains its perfect condition ; the at first short, 

 soft, thick wings spread in the course of a few minutes to their future 

 full size, then speedily dry in the air, when the at first distinct circu- 

 lation of the blood in the ribs gradually disappears, and the metamor- 

 phosis of the individual is completed. It raises itself with difficulty 



* The passage in inverted commas is a MS. alteration from the original, commu- 

 nicated bv the author. TR. 



