153 ORIGIN OF SOCIETY. CANTO iv. 



Swarm on each leaf with eggs or embryons big, 

 And pendent nations tenant every twig. 

 Amorous with double sex, the snail and worm, 

 Scoop'd in the soil, their cradling caverns form; 

 Heap their white eggs, secure from frost and floods, 

 And crowd their nurseries with uncounted broods. 

 Ere yet with wavy tail the tadpole swims, 

 Breathes with new lungs, or tries his nascent limbs; 3(30 

 Her countless shoals the amphibious frog forsakes, 

 And living islands float upon the lakes. 



The honey-dew on the upper surface of leaves is evacuated by these 

 insects, as they hang on the underside of the leaves above; when 

 they take too much of this saccharine juice during the vernal or 

 midsummer sap-flow of most vegetables ; the black powder on leaves 

 is also their excrement at other times. The vegetable world seems 

 to have escaped total destruction from this insect by the number of 

 flies, which in their larva state prey upon them; and by the ichneu- 

 mon fly, which deposits its eggs in them. Some vegetables put forth 

 stiff bristles with points round their young shoots, as the moss-rose, 

 apparently to prevent the depredation of these insects, so injurious 

 to them by robbing them of their chyle or nourishment. 



The tadpole swims, 1. 359. The progress of a tadpole from a fish 

 to a quadruped by his gradually putting forth his limbs, and at length 

 leaving the water, and breathing the dry air, is a subject of great 

 curiosity, as it resembles so much the incipient state of all other 

 quadrupeds, and men, who are aquatic animals in the uterus, and 

 become aerial ones at their birth. 



