SIR JOHN LUBBOCK ON THE ANATOMY OF ANTS. 149 



They consist of a number of branched and twisted tubules which gradually unite in a 

 single duct. This duct then swells into a capacious receptacle, after which it contracts 

 again, and after joining the corresponding duct from the other side, passes through the 

 neck into the head, and then, after a meandering course, opens at the upperside of the 

 under lip. The duct consists of an epithelial layer of cells, within which is a structureless 

 membrane, strengthened, as is so often the case with the ducts of glands, by chitinous 

 ridges, which give it very much the appearance of a trachea. Fig. 3, PI. XI., represents 

 a glandular organ situated in the lower part of the thorax of Myrmica ruginodis imme- 

 diately above the base of the anterior leg. 



Mesotliorax and Middle Legs. 



The mesotliorax is much more closely connected with the metathorax than with the 

 prothorax (PL XI. fig. 2). Like the prothorax it consists of an upper and lower more or 

 less arched plate. The upper plate or mesonotum (PI. XL figs. 2, 5, 6, lies) is oblong, 

 somewhat emarginate behind, the spiracles (PI. XL figs. 2, 4, Sj) 2 ) being situated at the 

 posterior angles. In front the mesonotum projects some way over the sides of the pro- 

 thorax ; and as the middle legs are attached quite at the posterior end of the metapectus, 

 they, as well as the posterior legs, lie under the metanotum, and seem at first sight as if 

 they belonged to the hinder division of the thorax. 



The depressor of the prothorax (PI. XL figs. 2, 4, 5, in) arises from the junction of the 

 meso- and metathorax, beneath the spiracle, and passing down and forwards is attached 

 to the lower posterior edge of the prothorax, which therefore it would tend to draw 

 downwards. 



On the other hand, the elevator of the prothorax (PL XL figs. 2, 5, n) rises from the 

 upper part of the antefurca, and passes backwards and downwards to a spur of the 

 medifurca just above the mesothoracic ganglion. 



The second pair of legs has, according to Straus-Durckheim's description of Melolontha, 

 three flexors and two extensors. The arrangement, however, is very different from that 

 in the Ant. 



Graber, in his excellent work, refers specially to four muscles ; the first (irfm, in his 

 fig. Gl) rises from the central ridge of the sternum, and, passing directly outwards, is 

 attached to the inner edge of the coxa, Avhich therefore it would draw inwards and 

 downwards. The next two (slim 1 and 2, in his fig. 61) rise one behind the other from 

 the side of the thorax, and would, on the contrary, draw the leg outwards and upwards. 

 The fourth also lies behind the other two, but would specially draw the leg upwards. 



As regards the Ant, the principal muscles which move the middle legs are shown 

 in PL XL fig. 4, PL XII. fig. 2. 



The first muscle (o, PL XL figs. 4, 5, and PL XII. figs. 2 & 5) rises partly from the 

 upper lateral wall of the mesonotum immediately under the spiracle, partly from the 

 medifurca, and passing downwards contracts into a tendon which is continued into the 

 leg. It would tend to raise the leg. 



The second rises from the anterior edge of the medipectus (PL XII. fig. 2, p), and 

 passing straight back is attached to the anterior edge of the coxa. 



20* 



