162 TRANSFORMATION OF ANIMALS. 



of this instrument, makes incisions in the leaves or branches' 

 of a tree, and in each incision lays an egg. This egg is at 

 first extremely minute ; but it soon acquires a considerable 

 bulk, and the gall has arrived at its full size before the worm 

 is hatched. It is a singular and almost inexplicable fact, that 

 the eggs of gall-flies should continue to grow after being 

 separated from the body of the mother. But that their eggs do 

 augment in size ; that worms proceed from them ; that these 

 worms are nourished and live a certain time imprisoned in 

 the galls ; that they are transformed into nymphs or chrysalids ; 

 and, lastly, that they are metamorphosed into winged insects, 

 which, by gnawing an aperture through the gall, take their 

 flight in the air ; are known and incontestable facts, of the 

 truth of which every man may easily satisfy himself. Ex- 

 amine the common oak-galls, or those of any other tree ; if 

 any of them happen to have no aperture, cut them gently 

 open, and you are certain to find an egg, a worm, a chrysalis, 

 or a fly ; but in such as are perforated by a cylindrical hole, 

 not a vestige of an animal is discoverable. The galls, which 

 make an ingredient in the composition of ink, are thick, and 

 their texture is very strong and compact. That the small 

 animals they contain should be able to pierce through such a 

 rigid substance is truly wonderful. 



In the general order of nature among oviparous animals, 

 each egg includes one embryo only. A singular species of 

 eggs, however, discovered by the celebrated Mr. Folks, late 

 President of the Royal Society of London, must be excepted. 

 He found great numbers of them in the mud of small rivulets. 

 In size they equalled the head of an ordinary pin. They 

 were of a brown color, and their surface was crustaceous, 

 through which, by employing the microscope, several living 

 worms were distinctly perceptible. By dexterously breaking 

 the shell, he dislodged them ; and he found, with surprise, 

 that eight or nine worms were contained in, and proceeded 

 from, the same egg. They were all well formed, and moved 

 about with great agility. Each of them was inclosed in an 

 individual membranous covering, which was extremely thiri 

 and transparent. It were to be wished that the transforma- 

 tions of these extraordinary animals had been traced. 



Some caterpillars, when about to transform, make a belt 

 pass round their bodies. This belt is composed of an assem- 

 blage of silken threads, spun by themselves, the ends of which 

 they paste to the twigs of bushes, or other places where they 

 choose to attach their bodies. They likewise fix their hind 



