134 INSECT TRANSFORMATIONS. 



skin of this caterpillar, the following operation must 

 be used. One must kill a full-grown caterpillar, tie a 

 thread to its body, and dip it for a minute or two into 

 boiling water. The outer skin will, after this, easily 

 separate, because the tluids, between the two skins, 

 are by this means raretied and dilated, and therefore 

 they break and detach both the vessels and the fibres 

 wherewith they were united together. By this means 

 the outer skin of the caterpillar, being separated, may 

 be easily drawn oif from the butterfly which is contain- 

 ed and folded up in it. This done, it is clearly and 

 distinctly seen, that, within this skin of the caterpillar, 

 a perfect and real butterfly was hidden, and therefore 

 the skin of the caterpillar must be considered only as 

 an outer garment, containing in it parts belonging to 

 the nature of a butterfly, which have grown under its 

 defence by slow degrees, in like manner as other sen- 

 sitive bodies increase by accretion. 



' J3ut as these limbs of the butterfly which lie under 

 the skin of the caterpillar cannot, without great diffi- 

 culty, be discovered in the full-grown caterpillar, unless 

 by a person accustomed to such experiments, — because 

 they are then very soil, tender, and small, and are 

 moreover complicated or folded together, and inclosed 

 in some membranaceous coverings, — it is, therefore, 

 necessary to defer the operation just now proposed, 

 until the several parts of the butterfly become some- 

 what more conspicuous than at first, and are more 

 increased and swelled under the skin by the force of 

 the intruded blood and aqueous humour. This is 

 known to be the case when the caterpillar ceases to eat, 

 and its skin on each side of the thorax, near under the 

 head, is then observed to be more and more elevated 

 by the increasing and swelling limbs, and shows the 

 a])pearance of two pairs of prominent tubercles.'* 



* Swammerdam, Book of Nature, ii, 26. 



