ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 221 



the lower lip, upper lip, and hypopliarynx as the proboscis proper. 

 The former is, superiorly, provided with a pair of simple palps, which 

 appear to be the remnants of the mandibles, the latter has on upper 

 side a deep longitudinal groove, in which lie, one above the other, the 

 two unpaired chitinous stilets. 



The upper of these appears to be the direct prolongation of the 

 superior and anterior edge of the cephalic cone ; the free portion can 

 be bent, but the basal part is connected with the head. The hypo- 

 pharynx is a longitudinally compressed hollow cone, and its groove, 

 opposite to that of the upper lip, unites with it to form a tube which 

 opens into the digestive canal ; it is traversed internally by the ducts 

 of the thoracic salivary glands, which open at its tip ; the true mouth- 

 opening may be regarded as being placed at the anterior end of the 

 small chitinous capsule, and at the point where the upper lip and 

 the hypopharynx are inserted. The lower lip does not, as in other 

 Diptera, or in Hemiptera, form the true sucking tube, but is a support 

 for it. After describing in great detail all the accessory points, the 

 author passes to the musculature and the mode of action of the 

 proboscis. 



The proboscis is drawn into the head by two pairs of muscles, and 

 these, in retracting, cause also a flexion of the lower lip ; these strong 

 muscles are aided by two pairs which are less well developed, and 

 one of these seems to effect the double folding which is to be noticed 

 in the basal membrane of the cone. While the action of the above- 

 mentioned muscles is not difficult to understand, it is less easy to see 

 how the protrusion of the proboscis is effected. What is wanted in 

 the way of fulcrum for the muscles seems to be made up for by the 

 disposition of the tracheal system of this region ; the limbs which 

 enter the head swell out into (apparently two) large vesicles, which, 

 when the proboscis is protruded, occupy the whole of the internal 

 cavity, so far as this is not occupied by the nerve-centres, optic nerves, 

 and cephalic vesicle. When these contract, room is made for the 

 inpressing fulcrum, without any disturbance of the surrounding 

 organs. 



Special movements appear to be confined to the upper lip ; it is 

 straightened out by a delicate pair of muscles, which are opposed by 

 another pair, whose chief function would appear to be to bring into 

 contact the two halves of the sucking groove. The movements of the 

 labella are next described, and then the process of sucking is taken 

 up ; a fly is not only able to take in fluid, it can also feed itself on 

 solid matters suspended in liquid. This injection of material appears 

 to be effected on the method of the suction-pump, the movable piece 

 being represented by the upper plate of the base of the fulcrum, 

 which, as it is drawn up, carries the fluid into the fulcral canal ; the 

 depression of this plate drives the nutriment to either side, unless the 

 anterior portion of the plate has descended first and so formed a kind 

 of safety-valve, in which case the fluid passes backwards into the 

 oesophagus. 



Solid substances are dissolved by the action of three pairs of 



