CABBAGE WHITE BUTTERFLIES 169 



reality gradual ; the new organs are slowly developed 

 and grow by imperceptible degrees. When the 

 animal becomes to outward appearance transformed 

 in a night, it is because the new parts have been 

 concealed by the old skin, and are suddenly revealed. 



Malpighi and Swammerdam knew all this as well 

 as we do. Swammerdam tried to make it plain to 

 his contemporaries, but in spite of his earnestness he 

 only succeeded in a moderate degree, so much were 

 men's words and thoughts entangled with the 

 mischievous theories of bygone ages. 



The reader will be glad, I dare say, to quit these 

 ancient controversies and get back to matters of fact. 

 We have seen that Malpighi and Swammerdam 

 nearly at the same time discovered the rudiments of 

 the imago within the caterpillar. The following in- 

 structions are based upon Swammerdam's method of 

 procedure. Take a full-grown larva of any Moth or 

 Butterfly which has ceased to feed, kill it with ether, 

 tie it dawn with thread, and dip it several times in 

 boiling water. The outer skin will then peel off 

 readily, and the Butterfly will be exposed to view. I 

 have repeatedly done what Swammerdam recom- 

 mends, and have seen what he describes. When the 

 larval skin is removed, we find a flabby, pale-coloured 

 object left behind, which has two pairs of short and 

 crumpled wings, three pairs of legs folded beneath 

 the thorax, a pair of long antennae, and a pair of long 

 and slender mouth-appendages. Except that they 

 are soft, wrinkled, and somewhat undersized, all these 

 parts agree perfectly in outward form with the wings, 

 legs, antennae and maxillae of the Butterfly. The 



