INTRODUCTION. 29 



a piece of wood, the earth, the water, a putrid substance, 

 the body of a living animal, or that of another insect. 

 The species of tree or of animal is never mistaken. 

 The pulex penetrans, or chigoe of the West Indies, de- 

 posits her progeny in the human body. The oestrus 

 bovis, or gadfly of the ox, seeks no nidus for hers, but 

 beneath the skin of that animal ; and that of the horse, 

 fastens her eggs to the hair of the animal, and then 

 tickles and irritates the skin in such a manner as that it 

 may, by applying its mouth to the place, take the eggs 

 into the stomach. Even in those cases where the 

 animal, or egg, or whatever else is to be the nidus, and 

 supply the food, is to perish by the operation, the de- 

 struction does not take place until the young animal 

 has perfected its growth, and escaped, to pass into an- 

 other state. 



In their mechanical structures, whether for their own 

 habitations, for their young, or as snares to assist them 

 in procuring their food, we have still the same unifor- 

 mity. In those that form themselves into societies, as 

 the beaver, the bee, and the ant, we find the one assist- 

 ing the other ; but we never find any teaching, or any 

 need of it. Beavers build all in the same way, in 

 similar situations, and, where they can procure them, 

 of the same materials. All bees, of the same species, 

 construct their cells in the same form; and if their 

 wax and their honey be not exactly the same, the 

 difference may always be traced to the plants from 

 which those substances are collected. In all these 

 wonderful habits they are perfectly regular. These 

 form part of the grand system of which the elements 

 and the seasons form a part ; and none of them varies 

 D 3 



