380 LECTURE XVII. 



A. Salivary vessels which open into the mouth, generally beneath 

 the tongue, sometimes at the base of the mandibles. They take the 

 following forms : — 



1. As simple, long, undivided, twisted tubes ; thus in the majority 

 of insects, viz. all butterflies, many beetles, and flies. 



2. As a narrow vessel which empties itself into one or two 

 bladders, whence the salivary duct originates {JVepa, Cimex, Sarco- 

 phaga). 



3. As a ramose vessel with blind branches (Blaps). 



4. As two long cylindrical pipes, which unite into one excretory 

 duct (lieduvius). 



5. As four small, round bladders, each pair of which has a common 

 duct (^Pulex, Lygceus, Cimex). 



6. As a multitude of such vesicles (JVepa). 



7. As capitate tubes, in the free ends of which many very fine 

 vessels empty themselves ( Tabanus). 



8. As tubes which at intervals are surrounded by spiral caeca 

 ( Cicada). 



9. As granulated glands, which on each side unite into a salivary 

 duct, both of which join into a single excretoi'y duct. Miiller has 

 observed this high form of conglomerate salivary glands in Phasma ; 

 Treviranus in Apis ; and Burmeister in Locusta, Gryllus, and 

 Termes, 



Some Entomologists ascribe a hepatic function to the closely ag- 

 gregated cells forming the internal tunic of the chylific stomach, and, 

 with more reason perhaps, to similar cells in the csecal appendages 

 of the stomach, when these are present. A pancreatic function is 

 assigned to certain glandular appendages to the ilium, as e. g. to the 

 two or four rows of follicles in that of some bugs (Pentatomidce), 

 and to the ramified appendages below the gastric (hepatic ?) cceca in 

 the mole-cricket {Gryllotalpa). There are, however, secerning 

 organs, in the condition of long, slender, cylindrical tubes, such as 

 Cuvier, who seems not to have been aware of the conglomerate 

 structure of certain salivary and seminal glands, describes as the 

 character of all the secreting organs in insects, which tubes have a 

 degree of constancy more befitting the important excretory and 

 accessory digestive functions of a liver, than the exceptional cha- 

 racter of the parts above cited. 



These tubes are called " Malpighian," after their discoverer.* In 

 a few instances, as Coccus, Chermes, and Aphis, they are wanting : in 

 almost all insects they are four in number, never fewer; sometimes 

 they are six or eight in number : in a few instances, as the mole- 



* CCCXXII. 



