THE society's NOTE-BOOKS. 115 



I. — The mandibles in the Hymenoptera and Neuroptera when 

 they are highly developed are attached to the cheeks. In the 

 Empis the organs in question are attached to a piece, which is 

 jointed on to the clypeus, and beneath which is the lingua (a large 

 dagger-like organ, the end of which is correctly indicated in 

 Mr. West's figure by the letters /g.) This is the position occupied 

 by the labrum in most insects. 



2. — The extremity of the labrum is frequently variously cut and 

 notched in the diptera, and is frequently extremely prolonged in 

 the Tabanus, or Horse-tiy. 



3. — The organs in question do not appear in the living insect 

 as represented in Mr. West's figure^ in which they have been 

 flattened out. In the living insect the bristles (not teeth) with 

 which the outer edge of the organs in the figure is armed are 

 beneath the organ, and parallel to each other — i.e., seen in profile, 

 not from above, so that when closed they form a kind of net. 



In one instance (a neuropterous insect, the name of which I 

 do not know) the head is prolonged into a snout, and the 

 mandibles are at the extremity, but in this case the maxilte, and 

 lingua, and labium, are all also at the extremity of the snout. If 

 this, then, be an instance of the mandibles at the end of a snout, 

 and the other parts attached to the base, it is the only instance I 

 have met with in any order. Geo. Crewdson. 



Hybos grossipes belongs to the very large family of Euipidce. 

 — The Empidae are common in the spring and early summer; 

 towards autumn they become rarer. They are a very interesting 

 family on account of the peculiarity of their mouths and antennce. 

 Let alone the general build of the fly, an Empis can always be 

 recognised by its antennas, which are invariably of the characteristic 

 " steeple" shape, (^t^ Journal Micro., Vol. IV., Pis. V. and VI., 

 Figs. 6 and 7.) H. M. J. Underhill. 



Slides of Crystals. — I do not agree with those members who 

 think that these slides " teach little." In my opinion, the forma- 

 tion of a crj'stal is a subject for deep thought. Let us suppose a 

 Cubic Crystal to be under inspection. As time goes on it increases 

 in size, but is still a cube ; how is it increased ? Is it by adding 

 layer to layer as we plaster the walls of our houses, or is it by adding 

 cube to cube as we build our chimneys by adding brick to brick ? 

 and if so, what was the size of the original germ ? In fancy I can 

 see it so very minute, that it may be fairly described as a square 

 mathematical point having neither length, breadth, or thickness, 

 and yet consisting of a solid, enclosing the water of crystallisation, 

 and these are the bricks which form the slides of Asparagine, San- 

 tonine, and Salicine. A. Nicholson. 



