THK METAMORPHOSIS. 433 



255. 



The changes which take place within the larva during the several 

 moultings are unimportant. But formerly, where we spoke of the 

 changes which the intestinal canal and the sexual organs undergo 

 during the metamorphosis ( 114 and 143), and which we have since 

 recently referred to, we noticed that the changes of these organs com- 

 mence only during the pupa state, and that consequently the cater- 

 pillar retains the same form of the intestinal canal and the same figure 

 of the sexual germs, and that both merely increase with its growth, in 

 compass and in the structure of their tunic. But, upon the larva pass- 

 ing into the pupa state, a change of the internal organs takes place, as 

 well as of the external figure. These changes we have indicated at the 

 above place, but those undergone by the larva we explained earlier 

 ( 60) ; it, therefore, merely remains for us to make a few observations 

 upon the character of these transformations. 



With respect to form, by it the law laid down by Von Bar, of a 

 progression from a general to a particular figure during development, 

 receives full confirmation. The intestine of the larva is simple, broad, 

 generally straight, and without many convolutions ; its divisions are not 

 strongly marked, but pass gradually into each other. During the pupa 

 state, however, it transforms itself to a longer, much convoluted tube, 

 separated into several divisions, which now exhibit a distinct difference 

 of texture ; and indeed new organs are added of which there was 

 formerly no trace, namely, the proventriculus in the Carabodea, the 

 sucking bladder and caecum in the Lepidoptera, the villi in the ilium 

 of the flesh eaters, &c. In the flies, in which indeed the intestine upon 

 the whole shortens, each individual division, however, and particularly 

 the ilium, acquires a more determinate form and a more compact struc- 

 ture ; the sucking stomach more distinctly separates itself, its orifice 

 lengthens, as also does the oesophagus. In the sexual organs there is 

 a more distinct difference of structure : parts which previously had a 

 great resemblance to each other, namely, the testes and ovaria, from 

 day to day increase in dissimilitude ; and other organs, of which before 

 there was no indication, gradually form themselves from simple pro- 

 cesses to long convoluted canals ; lastly, the pupa itself exhibits a vast 

 discrepancy of form. The larva was a worm composed of equally large 

 rings ; the pupa, on the contrary, possesses the entire form of the sub- 

 sequent insect, and differs, therefore, with respect to the forms of its 

 rings chiefly by the difference of size found between several, namely, 



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