134 INSECT TRANSFORMATIONS. 



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

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

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

 separate, because the fluids, between the two skins, 

 are by this means rarefied and dilated, and therefore 

 they break and detach both the vessels and the fibres 

 wherewitli they were united together. By this means 

 the outer skin of the caterpillar, being separated, may 

 be easily drawn off from the butterfly which is contained 

 and folded up in it. This done, it is clearly and dis- 

 tinctly 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. 



" But 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 soft, 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 appearance of two pairs of prominent 

 tubercles*." 



Swammerdam, Book of Nature, ii. 20. 



