HARDWICKE'S SCIENCE-GOSSIP. 



159 



where it abuts on the part to be next described, and 

 at the posterior extremity it is broadened and 

 turned upwards, the two posterior corners forming 

 knobs for the attachment of muscles. The anterior 

 portion is united to the upper side of the raentum, 

 and it is connected behind by a short membranous 

 tube to the pharynx. At its anterior extremity, a 

 minute eminence marks the surface of the salivary 

 duct, and is the only representative of the tongue I 

 can detect. This duct extends as a single tube 

 through the head at the base of the braiu, after 

 which it divides, and leads to two small salivary 

 glands situated in the thorax ; it may easily be mis- 

 taken for a tracheal tube, but the rings are not so 

 regular and perfect as in the latter, and near its 

 extremity they assume a longitudinal instead of a 

 circular direction. 



Immediately in front of the floor of the mouth is 

 a narrow thin plate,* which marks the line of 

 division between the lobes ; it is the third portion 

 of the labium as above enumerated, the fourth and 

 last being the lobes themselves. These are attached 

 above the plate just mentioned, and are connected 

 below with the anterior edge of the mentum. Their 

 external surfaces are of a thickened miscellaneous 

 texture, strengthened by a thick clothing of fine 

 hairs, between which are interspersed others of a 

 much larger size, and furnished with bulbous roots. 

 A pair of narrow horny plates extend across them 

 about the centre of their length, from the superior 

 to the inferior surface ; immediately behind which 

 is another larger pair of a somewhat triangular 

 shape, the posterior angles of which are connected 

 by a complicated articulation with a handle-like 

 internal process, which arises from the junction of 

 the mentum with the base of the lobes. These 

 parts together form a protective covering for the 

 more delicate structure which ordinarily lies folded 

 up between them. When expanded, however, 

 this is seen to be a membranous sac, ornately marked 

 with a fine tracery of false tracheal tubes ; it is the 

 essential feature in this part of the organism, not 

 perhaps so elaborate in its details as that of the 

 Blow -fly, but nevertheless forming a very beautifal 

 and instructive object for microscopic display. The 

 false tracheae, as they are called, are deep-channelled 

 folds in the transparent membranes, kept open by 

 incomplete rings, which dilfer from those of the 

 Blow-fly in being perfectly plain, instead of, as in 

 the latter insect, forked at either end alternately. 

 Four main channels arise immediately in front of 

 the floor of the mouth, two on either side, and, 

 gradually decreasing in size, take a sinuous course 

 over the bladder-like membrane ; from these a 

 great number of smaller similar channels diverge 

 at right angles, covering the whole surface of the 



* I think this is the anterior labial plate of Mr. Lowne. 

 (Seep, 47.) 



organ, and forming a fine strainer, through which 

 the fluid element of the insect passes on its way to 

 the mouth. A pair of small chitinous hook-like 

 thickenings of the integment, may be seen in front 

 of the floor of the mouth, one on each side the 

 origin of the false trachete, which are, I believe, the 

 homologues of similar booklets, which in the Blow- 

 fly Mr, Lowne thinks may represent the mandibles,* 

 The articulation of the base of the lobes with the 

 anterior edge of the mentum presents several 

 complicated parts which I have not been as yet 

 able fully to understand ; but the following may I 

 think be made out, A stout handle-like internal 

 process is borne by the base of the lobes between 

 the posterior lateral plates, immediately over the 

 slender rod-like process of the mentum before 

 mentioned, and between it and the floor of the 

 mouth ; it »is not so long as the process of the 

 mentum, but like it, serves for the insertion of 

 muscles, a pair of which are attached to its posterior 

 extremity, and connect it with the back of the head : 

 these seem to be retractors of the mentum and 

 lobes, but how the converse movement of their 

 protrusion is effected, I am unable to suggest. 

 Another pair of muscles directed forwards are also 

 attached to the posterior extremity of this process, 

 and connect it with two small plates on either side 

 of its anterior extremity, which form part of the 

 complicated articulation above alluded to. 



III. The masillffi, and the maxUlary palpi, wil 

 next claim our attention. The former are, I believe, 

 represented by two stout joint-like pieces on each 

 side of the mentum from which the four jointed 

 palpi spring. I confess it was some time before I 

 could understand these organs at all, and I feel I must 

 even now speak dilfidently on the subject. If the 

 reader will turn again to Mr. Lowne's description of 

 the mouth of the Carpenter Bee in the number for 

 Oct. last, he will find the maxillae of that insect 

 described as follows: — "Each consists of a large 

 outer knife-shaped lobe mx, strengthened by a 

 prominent rib along its inner margin ; of a small 

 inner lobe densely covered with sensory hairs mxr ; 

 of a basal sheath mxb, and a rudimentary palpus 

 inxj}." Now I think that the minute horny rods 

 before alluded to as existing in the integument on 

 each side of the labrum in the fly, are homologous 

 to the more highly developed and "knife-shaped 

 lobes " of the maxillae of the bee ; that the joint- 

 like basal pieces of the fly are the homologues of 

 the " small inner lobes," and the " basal sheaths " 

 of the bee, the palpi, which are so enormously deve- 

 loped in the former insect, being reduced to mere 

 rudiments in the latter. My reasons for this 

 opinion have been already alluded to when speaking 

 of the labrum, and I will only now ask the reader 

 to accept this explanation in default of a better. 



* Lowne's "Anatomy of the Blow-fly," p. 47, 



