44 ON THli ANATOMY OF THE FLY. 



part iii tlie perfect insect to doubt its homology. The small 

 straight appendages II, appear to belong to this organ, which 

 supports them, and to represent the maxilla). I am even inclined 

 to believe the superior ventral processes of the sucking organ 

 are the homologues of their apodernes, No connection can, 

 however, be absolutely traced between these parts in the larva 

 and perfect insect, as all parts of the mouth of the former remain 

 attached to the pupa case, but I am inclined to believe this is a 

 mere shedding of integument, arid that the new organs of the 

 mouth are directly dependent for their formation upon the old, 

 like the abdominal segments and the whole digestive system.* 



The second segment of the proboscis ( Plate III ) folds upon 

 the basal one with an elbow-like joint, so that their dorsal sur- 

 faces arc in contact when the organ is at rest. The maxillary 

 palpi then lie against the edges of the oral cleft, and are directed 



DESCRIPTION OF PLATE III. 



This plate represents the right half of a vertical section of the proboscis 

 a little to the left of the mesial line, a, The pharynx, cut through above but 

 not divided vertically. 6, The operculum, with one of its apod^mep, which 

 may be traced behind the pharynx, c, The labium, which forms the floor 

 of the mouth and is continuous above with the salivary tube, rf, Half 

 the mentum. e, Band supporting the scale-like lobe of the maxilla, 

 several setae, and the maxillary palpus. /, Valve in the salivary duct. 

 g, Great tracheal sac giving off the main tracheal vessel, which supplies 

 the muscles of the canula and lobes. ^, The lobes, with some of the hex- 

 agonal pigment cells shown as well as the spherical cells, to which the 

 greater portion of the main nerve which accompanies the principal 

 tracheal vessel is distributed, z, Chitinous band surrounding the trian- 

 gular opening of the mouth, which supports the false trachea? and the 

 teeth ; its anterior extremities bear a pair of curved hooks, probably the 

 homologues of the mandibles. A group of spherical cells, immediately 

 connected with a set of recurved hairs, is seen above this piece, with a 

 branch of the main nerve distributed to them. 



* Wcismann asserts ( Koll. Zeitschrift, Band. XIV. ) that the salivary 

 glands of the perfect fly are new formations, and that he once found the 

 salivary gland of the larva by the side of that of the perfect insect, in the 

 same imago ; I think, however, the malformation must be otherwise 

 accounted for. Sec Section III. page 51. 



