hy some Insects upon Plants. 183 



pointed at each end, the posterior tapered for a very considerable 

 space, contracting as it were by three separate gradations till it 

 terminates in a point ; the head end is something like that of an 

 eel, bluntish, and gradually widening out for a considerable way 

 backwards, where there is a greenish annulus, formed perhaps by 

 the commencement of the intestines, as behind this there is a 

 cloudiness all along the middle. I could not perceive the oral 

 opening, but behind the point there is a dusky spot connected 

 by a line with the interior. The young ones are immaculate 

 white, but the old contain a profusion of greenish granules, 

 which may be either the eggs or the undigested food. Although 

 not indicated externally, the body is evidently com])osed of a 

 series of rings which separate the internal contents ; as one in 

 which the skin happened to be ruptured was emptied in a man- 

 ner corresponding to this structure. The movement of the par- 

 ticles at the wound was a rapid rush, which extended itself by 

 degrees upwards ; but there were intervals where the current 

 seemed to be impeded as if by constrictions, upon passing which 

 it again flowed freely. The worms placed in moisture agitate 

 themselves to and fro, but are usually rather inactive. The length 

 is about 1 line. The species is probably new, and may be called 

 Vibrio Graminis. 



According to the observations of Mr. Bauer, Vibrio Tritici is 

 originally introduced, in the young or egg state, into the germi- 

 nating seed-corn, and after a succession of generations during 

 the passage, is conducted by the propulsion of the circulating 

 fluid up higher and higher, till it reaches the ear. Whether this 

 be the means by which the present species gains access to the 

 position which it occupies, I cannot determine. It is by no means 

 uncommon, and as the parts affected by its presence dwarf the 

 blade, interfere with the healthy flow of the sap, and will pro- 

 bably soon decay, it may be regarded as somewhat prejudicial to 

 the coast pastures, which are principally composed of the grasses 

 that it attacks. The granules with which the knots are filled 

 give out a brown tincture when moistened. 



2. Cecidomyia of the Willow, Rose, and Rock-rose. 

 It has recently been discovered by the German naturalists, that 

 several of the galls which the Cynipides originate upon the leaves 

 of trees produce two different forms of gall-fly ; it has not how- 

 ever, so far as I am aware, been remarked, that the galls formed 

 by the Dipterous Cecidomyioe may in like manner be colonized 

 at one and the same time by distinct species. The rose-gall upon 

 the summits of willow shoots has attracted the attention of most 

 observers, and DeGeer has briefly indicated the fly {Cecidomyia 

 salicina), which he reared from the red larva which occasions it, as 



