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made by all the various Arthropoda that have the habit. Inch- 
bald, Hardy, Miller, and Meade have also published important 
papers on British Gall-Midges. 
The galls on the Lime are produced on the flower stalks, 
in the form of a round or ovate swelling, at first pale green in 
colour, but as they reach full size tinged with reddish pink. They 
are inhabited each by a single larva; but it is very common to 
find two or more galls so close to each other that in time they 
merge together and form a large bunch of galls ; while the abor- 
tion may include all the flower pedicils, and prevent the formation 
of any perfect flower at all. 
On making continuous sections of the gall, the larva is 
found occupying a cavity, which it almost completely fills, in the 
very centre of the fibro-vascular bundle of the stalk. This 
portion of the plant, and indeed the whole tissues of the stalk 
at the affected spot, have undergone important changes. A 
- comparison with a normal fibro-vascular bundle shows that its 
vessels have been partially obliterated by the thickening of the 
walls of all the cells; the bundle instead of showing cells of 
different structure as usual, consists in fact of fairly uniform 
thick-walled cells, apparently thickened, and increased in 
number radially, to compensate the disability caused by the 
pressure of the foreign element. The cells of the parenchym 
are stretched out of their normal shape and assume forms such 
as would be the result of tension, due to pressure from within ; 
those of the epidermis are similarly pushed out of shape. 
It would appear that mainly, if not entirely, the bulk of the 
additional material forming so large a swelling as the full sized 
Gall, quite 4 or 5 times the diameter of the normal stalk, is 
made up of altered fibro-vascular tissue. 
Drawings of the section would of course convey a better 
idea than mere description, and a subsequent paper will, I hope, 
contain accurate illustrations of the various changed tissues of 
these galls, as well as of other species which I have examined. 
It has been remarked by Winnertz that “a want of horny 
organs of mastication (in the larve), authorizes the supposition 
that a lesion of the plant does not take place, more probably 
