62 METAMORPHOSES OF MAN 



days before it passes into the chrysalis condition, we 

 shall discover the rudimentary wings and antennae. 

 If at this period we cut off the little scaly feet, we 

 shall find that when the butterfly emerges from the 

 case, its legs will be imperfect. 



Hereafter we shall recur to these facts : suffice it 

 to say here, that the metamorphosis of the Pieris is 

 gradual, not sudden; and that in this, as in every 

 other instance, nature does nothing per saltum. We 

 shall see presently that this conclusion, which is suffi- 

 ciently demonstrated by an external examination, is 

 further borne out by dissection. 



Laying aside the internal changes which we have 

 already alluded to, we shall consider neither the sub- 

 cutaneous muscles nor those which are connected with 

 the chewing apparatus, false feet, &c, and which dis- 

 appear with them. We shall also avoid those associated 

 with the existing limbs and the movement of the 

 wings. We shall not refer to the hundreds of nervous 

 trunks and filaments, to the numerous branches and 

 ramifications of the tracheae, which spring into exist- 

 ence and disappear with the organs they are distri- 

 buted to. We shall confine ourselves to the study of 

 Herold's beautiful researches on the metamorphoses of 

 some of the large apparatus, and more especially of 

 the digestive tube and nervous centres.* 



The digestive apparatus which this caterpillar presents 

 when it first springs from the egg, and even when it com- 

 mences its transformation, is very simple in character. 



* " Entwickelungsgeschichte der Schmetterlinge," 1815. In this 

 splendid work, which even at the present day may be considered 

 a model, the author takes the pieris we have been examining as an 

 illustration. 



