u 



HARDWICKE'S S CIE NCE-GOS SIP. 



to which a few hairs are attached. The maxillae are 

 of an irregular shape; they are situated just 

 beneath the mandibles, and are surmounted by two 

 minute papilla?, which may represent the maxillary 

 palpi. 



The salivary glands and duct, as they open into 

 the mouth, are the first portions of the digestive 

 organs that claim our attention. The former are 

 two membranous sacs which lie immediately be- 

 hind the head, one on each side of the oesophagus. 

 They are bent back in a loop upon themselves, and 

 are lined with a delicate nucleated epithelium. A 

 ringed tube, somewhat like a large trachea, issues 

 from each gland, and these soon join in one, forming 

 the common salivary duct, which opens into the 

 mouth. The digestive canal commences with the 

 oesophagus. This is a slightly -bent membranous 

 tube, which, passing through the head and the 

 oesophageal nervous ring, terminates in a bell-shaped 

 cavity — the proventriculus. This tube has an 

 internal coat of structureless membrane, surrounded 

 by a muscular one of stout circular muscular fibres. 

 Between the two is a layer of what appears to be 

 formative plasma, containing a number of delicate 

 spherical nucleated cells. The inner coat exhibits 

 fine longitudinal striae, which are, I think, nothing 

 but minute folds. The oesophagus terminates pos- 

 teriorly in the proventriculus, where it forms what 

 may be called the clapper of the bell, as it projects 

 some distance into its interior, the inner lining 

 membrane being reflexed upon itself, so as to form 

 the walls of the latter organ. The proventriculus 

 terminates by a slightly constricted orifice in the 

 stomach, and also in four short blind bags or caeca, 

 the homologues of those which exist in the maggot 

 of the Blow-fly, though in the latter insect they are 

 much longer. The stomach is a tubular organ, and 

 extends from the proventriculus to the opening of 

 the bile-tubes. The walls of the proventriculus 

 and stomach are similar in character, and, like those 

 of the oesophagus, consist of an internal membra- 

 nous and an external muscular coat ; the former, 

 however, is thinner than in the oesophagus, and the 

 latter consists of an internal layer of circular, and 

 an external one of longitudinal, fibres. Both these 

 are finer than those of the oesophagus, especially the 

 former, where the characteristic striae seem almost 

 lost, at least with the optical power at my command. 

 Some of the longitudinal fibres pass from the ends 

 of the caeca, and form muscular bands, connecting 

 these organs with the walls of the stomach. A few 

 delicate cells, like those on the oesophagus, may be 

 seen between the membranous aud muscular coats. 

 The internal surfaces of the proventriculus and 

 stomach are lined with a layer of cylindrical epi- 

 thelial cells, easily detached from each other and 

 from the wall of the stomach : perhaps these 

 secrete the gastric juice.' On I he epithelial lining 

 I have frequently found minute organisms, which I 



believe to be the parasitic protozoon described by 

 Dr. Carpenter as the Gregarina ; but as the speci- 

 mens in which I found them had all been kept in 

 spirits, I, of course, could not observe whether 

 they had independent life or not. The cavities of 

 the proventriculus and stomach are filled with a 

 dark brown fluid, which exudes in great quantities 

 in freshly-killed insects when the walls are ruptured. 

 They are also occupied by a tangled mass of exuviae 

 separating the half-digested food-contents from the 

 epithelial liniug, and entirely unconnected with any 

 portion of the wall of the stomach. I believe it is 

 what indeed it much resembles, viz., a bundle of 

 cast-off clothes, the remains of successive moults, 

 which probably serve to protect the epithelial 

 lining from abrasion by the rough ends of grass, 

 fibres, &c, which fill the stomach. The external sur- 

 face of the stomach, especially at its upper portion, 

 is frequently covered with a number of round white 

 bags, varying from two or three to twenty, or more. 

 These are adherent to the outer muscular coat, and 

 have no connection at all with the stomach. They 

 are filled with fluid, in which float a great number 

 of minute corpuscles. I do not know at all what 

 these objects are, but think they are abnormal pro- 

 ducts, the result, perhaps, of disease, or of some 

 parasite. I am the more inclined to this opinion 

 from the circumstance that I have occasionally, 

 though rarely, found them absent. 



The biliary tubes open into the end of the 

 stomach. They are four in number, or, to speak 

 more correctly, two, since they anastomose in pairs, 

 and consist of long tortuous narrow tubes lying 

 between the intestines and the surrounding fatty 

 rete. Their course is first forward, towards the 

 head of the larva, and then backward, towards the 

 anus, where their convolutions are thickest. They 

 are filled iwith a brown granular fluid, with oval 

 cells. Below the opening of the biliary tubes, the 

 membranous wall becomes thicker, and is set with 

 minute spines ; the circular fibres of the muscular 

 coat also become much thicker and stronger, so 

 as to form a sphincter separating this from 

 the succeeding and terminal portion of the in- 

 testine, which opens on the anus. This is a large 

 sac, prolonged anteriorly towards the head into an 

 almost equally large blind process, or caecum, the 

 two together occupying as much space in the body 

 of the larva as all the rest of the digestive cavity 

 together. The membranous and muscular coats 

 which we have traced in the oesophagus and stomach 

 are continued also in this organ ; the fibres of the 

 latter are, however, more irregularly and sparsely 

 disposed than heretofore, except near the anus, 

 where the circular ones again become prominent, 

 forming a sphincter round the opening. The wall 

 of the sac often looks crumpled, as if drawn together 

 into pits by the action of the muscular fibres ; and 

 between the two coats, at least near the anus, there 



