222 SUMMARY OF CURRENT RESEARCHES RELATING TO 



glands, which, in a loose way, are sjpoken of as salivary ; the largest 

 and the best known of these lies in the thorax, and its secretion passes 

 into two ducts, which unite with one another in the head. This 

 unpaired duct passes along the lower side of the fulcrum, traverses 

 the hypopharynx, and opens at its tip. Just before it passes into the 

 hypopharynx the duct is provided with a simple valvular arrange- 

 ment, which regulates the supply of the fluid ; there is not, however, 

 any reservoir in connection with this valve, as was imagined by 

 Meinert, nor is there any pump-like arrangement, such as is found in 

 the Hemiptera. A second pair of salivary glands lie at the base of 

 the knob of the proboscis, and form large-celled rounded spheres ; the 

 ducts of these glands have, notwithstanding the investigations of 

 Graber, Meinert, and Becher, never yet been discovered ; after much 

 trouble the author was able to find their common orifice at the tip of 

 the superior plate of the lower lip ; each gland gives off a bundle of 

 fine canals, which finally open into a common efferent duct. The 

 third set of glandular cells which lie near the oesophagus are not 

 provided with a common duct ; they open by numerous canaliculi into 

 the oesophagus. 



Where the proboscis is not covered by thick chitinous plates it has 

 very thin and short hairs, which are mere projections of the chitinous 

 investment, and are neither hollow nor provided with nerves. In 

 addition to these there are tactile hairs, glandular setse, and gustatory 

 organs. 



The hairs are chiefly developed on the upper edge of the labellar 

 cushions, and have the form of delicate hollow hairs provided with 

 a fine nerve which arises directly from a multicellular ganglion. 

 With these hairs Krapelin would associate the hairs which have 

 been described by previous authors, and which are placed in two 

 longitudinal rows on the upper lip and pharynx. They do not 

 appear to have, as has been supposed, the function of gustatory 

 organs, but are rather means by which the firm particles that are 

 sucked in may be felt and retained. 



The glandular hairs are especially well developed on the outer 

 surface of the labella, and are distinguished by their enormous size ; 

 they are cylindrical in form, and have at their base a pyriform thin- 

 walled structure in which a number of rounded cells are inclosed as 

 in a sac. The author cannot agree with Kiinckel or Gazagnaire in 

 ascribing a nervous character to these bodies, inasmuch as the deep 

 grooves which are found on them speak rather to their glandular and 

 excretory function. 



The gustatory organs are placed on the inner face of the labellar 

 cushions, and each forms two pale concentric rings which do not 

 project above the integument, and cannot, therefore, have any tactile 

 function ; nerve-fibres, with a contained transparent axial cord, could 

 be made out in thin sections, and the relations of this demonstrated 

 clearly that it was a sensory organ that had to do directly with 

 chemical stimuli. The nerves which supply all the labellar organs 

 form two large limbs in the lower lip. The author hopes to extend 

 his investigations to other forms among the Diptera. 



