94 GENERATION OF INSECTS 



having a woody base and soft rim ; all these calices make 

 their worms, which come out in the shape of winged 

 animals. Hence, I have changed my opinion, and I think 

 it probable that the generation of worms in trees does not 

 occur fortuitously, nor does it proceed from the eggs 

 deposited by flies, especially as every gall or growth has 

 its own peculiar kind of worm, gnat, or fly, which never 

 varies. It is wonderful with what consummate skill Na- 

 ture forms the egg and prepares a place for it ; admirable 

 is the industry and patience with which she surrounds it 

 in a network of fibres and filaments, connecting it with 

 the gall, like so many veins or arteries, which furnish 

 the necessary supply for the formation of the egg and 

 the worm, and the indispensable nourishment of both. 

 Though there are different kinds of galls which produce 

 not only one, but many worms, still Nature knows where 

 they are and provides accordingly, as she does in the case 

 of prolific animals, which give birth to numerous young 

 at the same time. It is also to be noted that the worm 

 of the gall receives a certain vital stimulus from the oak, 

 for if such a growth should be pulled as soon as it ap- 

 pears on the tree, and when the eye cannot perceive any 

 sign of an egg, this gall will not produce a worm, nor 

 yet a fly. If the gall is plucked at a later stage, when it 

 is larger, and the first beginnings of the newly-formed 

 egg can be seen, and the taste is bitter, things will go 

 badly, and the worm will not reach maturity; but if the 

 worm does turn out well, it is because he has enjoyed a 

 full term of development that is invariable; though it is 

 true that different kinds of galls have different times of 

 maturity; in some the insects are ready for flight in the 

 Spring, others in Summer, Fall, or at the beginning of 



