182 THE MINUTE ANATOMISTS 



grow, he explains, just as much as any other animals. 

 Their changes of form are exactly analogous to the 

 changes by which a frog's egg becomes first a tadpole 

 and then a frog. But the frog has blood, and even 

 Harvey must have admitted that it grows. Swammerdam 

 loses patience when Harvey attributes to insects a meta- 

 morphosis which has nothing to do with growth, a kind 

 of transmutation, like that by which, it was supposed, 

 a base metal can be changed to gold ; an Ovidian meta- 

 morphosis, such as that by which a flying nymph is 

 turned to a laurel tree. The development of the 

 winged insect, says Swammerdam, is merely growth with 

 change of form, and the wings, legs and proboscis can 

 be discovered beneath the larval skin long before 

 the fly emerges. The insect is one and the same 

 animal throughout and has never been anything but 

 an insect. 



Swammerdam returns to the question again and again,^ 

 explaining how the legs, wings and other appendages of 

 a butterfly form beneath the larval skin, how they become 

 visible at the time of pupation, how they are glued down 

 till they have acquired due firmness, and how, having 

 cast yet another skin, they become functional when the 

 butterfly enters upon its free existence. 



In the section entitled " Animal in Animali," ^ Swam- 

 merdam shows how to demonstrate that the butterfly is 

 contained within the last larval skin. A full-fed cater- 

 pillar with swollen thorax must be taken and tied by a 

 thread to a stick ; it must then be time after time dipped 

 for a moment in boiling water until the skin becomes 

 loose, when it can be easily stripped ofi", leaving the 



1 See BiUia Naiurw, pp. 34, 578 (tortoise-shell butterfly), 603 (large cabbage- 

 white). 

 ' Biblia Naturae, p. 603. 



