BRITISH GALLS. 503 



the manner in which a model of a wagon and four horses can find 

 its way into a bottle, the neck of which is so small as to prevent 

 even the head of the wagoner from passing. The answer is sim- 

 ilar in both cases. The bottle was ingeniously blown over the 

 Wagon and horses, and the gall was formed around the grub. 



When the leaf is in its full juiciness, and the sap is coursing 

 freely through its textures, a little black insect comes and settles 

 Upon the leaf. She is scarcely as large as a garden ant, but has 

 four powerful and handsome wings, which can be used with much 

 agility. An entomologist, on seeing her, would at once pronounce 

 her to belong to the order Hymenoptera, and to be closely allied 

 to the ichneumon flies which have just been described. 



Running to and fro upon the leaf, she fixes upon one of the 

 nervures, and there remains for a short time, evidently busy about 

 some task, which is very important to her, but which her minute 

 pize renders impossible to be observed with the naked eye. If, 

 however, a magnifying-glass be applied very carefully to the leaf, 

 the following process will be seen. 



From the abdomen there projects a tiny hair-like ovipositor, 

 which is coiled in such a manner that it can be protruded to a 

 considerable length. This ovipositor is thrust into the leaf, so as 

 to produce a hole, which is widened by the action of the boring 

 instrument. Presently the blades of the ovipositor separate, and 

 a single egg is seen to pass between them, so that it is lodged at 

 the bottom of the hole. Into the same aperture is then poured a 

 slight quantity of an irritating fluid, and the insect flies away, hav- 

 ing completed her task. The whole proceeding, indeed,, is, with 

 the exception of the deposition of the egg, precisely the same as 

 that which takes place when a wasp uses its sting, the ovipositor 

 and sting being but two slightly different forms of the same or- 

 gan, and the irritating fluid of the cynips being analogous to the 

 poison of the wasp. 



The effect of the wound is very remarkable. The irritating- 

 fluid which has been projected into the leaf has a singular effect 

 upon its tissues, altering their nature, and developing them into 

 cells filled with fluid. As long as the leaf continues to grow, the 

 gall continues to swell, until it reaches its full size, which is neces- 

 sarily variable, being dependent on that of the leaf. I have, for 

 example, many specimens of these galls, of different sizes, from 

 which the insects have escaped, showing that they had attained 

 their full size. On the juices of the gall the inclosed insect lives 



