70 PERIOD III. 



by it. Man only can think ; animals are capable only 

 of physical sensations, and have no consciousness. 

 Into speculations like these we shall not venture, being- 

 content, like Locke, " to sit down in quiet ignorance 

 of those things which upon examination are proved to 

 be beyond the reach of our capacities." We shall 

 merely note here and there facts ascertained by obser- 

 vation or experiment, and plain inferences drawn from 

 such facts. 



Swammerdam and Reaumur, besides many naturalists 

 of less eminence, recorded a host of observations on the 

 activities of insects. They contributed little to the 

 discussion except new facts, for habit led them to ascribe 

 without reflection every contrivance to the hand of 

 Providence or else to Nature. Some of their facts, how- 

 ever, made a deep impression, none more than the exact 

 agreement of the cells of the honeycomb with the form 

 which calculation showed to be most' advantageous. 1 

 The coincidence has lost some of its interest since the 

 discovery that the theoretically best form of cell is hardly 

 ever realised. 2 R6aumur,3 in describing the process by 

 which a certain leaf-eating caterpillar makes a case for 

 itself out of the epidermis of an elm-leaf, showed that 

 the caterpillar is not devoid of that kind of intelligence 

 which adapts measures to circumstances. He cut off 

 the margin where the upper epidermis of the leaf passes 

 into the lower one, a margin which the insect had 

 intended to convert into one side of its case ; the cater- 

 pillar sewed up the gap. He cut off a projection which 

 was meant to form part of the triangular end of the 

 case ; the caterpillar altered its plan, and made that the 

 head-end which was originally intended to lodge the 



1 Reaumur, Hist, des Insectes, Vol. V., Mem. viii. 

 2 Darwin, Origin of Species, chap. vii. 3 Vol. III., Mm. iv. 



