i8 93 .] THE BRITISH NATURALIST. 91 



friends to whom he can refer. Having found the name of the plant, 

 the name of the insect is then, in most cases, an easy matter, for this 

 can usually be arrived at by the appearance of the gall, and as one 

 gall is generally very different from all other galls, the student has 

 thus an immense advantage over the student of some of the smaller 

 and more intricate groups of Coleopteva, Diptera, or Lepidoptera — say 

 the genera Homolota, Chironomous, or Gelechia. Then again, because 

 gall makers are distributed over several orders of insects, it is not 

 imperative that the student shall posses a full knowledge of all these 

 orders, for the gall makers are, as a rule, confined to certain well- 

 defined genera in each order. With regard to the preservation of the 

 galls, I think the cases exhibited show that by one means or another 

 all the difficulties in this way can be overcome. 



Now we come to the question " What is a gall ? " Let me try to 

 answer it. A gall, that is a vegetable gall (for there are animal galls 

 as well), is an excrescence of contorted cell growth, produced on a 

 plant by the agency of an insect (or insect ally) inside of which the 

 insect lives. A true gall entirely encloses the inmate ; a psendo-gall 

 only partially does so. 



" How is the gall produced ? " is a question to which no 

 satisfactory answer has yet been given. It is known, as I have 

 already said, that a gall is produced by an insect. It is also known 

 that the insect, with its ovipositor, pierces or punctures or slits the object 

 upon which it wishes to produce a gall ; and it is also believed that a 

 peculiar liquid is deposited in the opening where and when the egg is 

 laid, but this is as yet only a belief. And even if this be so, how such 

 a liquid acts in producing in one case a hard round marble, in another 

 a soft succulent cherry, and in a third a diminutive button, all from 

 the same leaf, the same kind of insect always producing the same 

 kind of gall, is to my mind, one of the greatest wonders of creation. 

 And what makes this still more wonderful is that the grub inside, as 

 pointed out by Kirby and Spence, seems to have nothing to do with 

 the building of the house it is destined to live in. The gall insect 

 " provided with an instrument as potent as an enchanter's wand, has 

 but to pierce the site of the foundation, and commodious apartments, 

 as if by magic, spring up and surround the germ of her future 

 descendents." Truly " there are more things on earth (not to mention 

 Heaven) than are dreamt of in our philosophy." 



A theory was brought forward by Newman, and very ably put by 

 him, that a gall is not an additional part to the plant on which it 

 grows, not a part that did not previously exist, but an existing part 

 modified for the purpose of a habitation. Thus one gall is a modified 

 leaf, another a modified bud, a third a modified stamen, and so on ; 

 and although this theory seems plausible in many cases, it is not 



