SIR J. LUBBOCK ON TUE ANATOMY OF ANTS. 



789 



into four distinct portions, in accordance with which there appear 

 to be four ganglia. 



The author then describes minutely the structure o£ the pro- 

 thorax from microscopical sections ; and a description in detail is 

 given of the muscles of the head and of the legs. 



The author calls attention to a structure in ants comparable to 

 that remarkable organ discovered by Yon Siebold (1844) in the 

 tibiae of the front leg of Gi'i/Uus, and considered by him to serve 

 the purpose of hearing. The recent researches of Dr. V . Graber 

 and others on this subject also receive due notice. 



In the tibia of Lasius flavus the trachea presents the following 

 arrangement. In the' femur it has a diameter of about ynyDU 

 an inch ; as soon, however, as it enters the tibia it swells to a 

 diameter of about yj-g- of an inch, then contracts again to -g-^^, and 

 then again, at the apical extremity of the tibia, once more expands 

 to 3-^. Moreover as in Gryllus, so also in Formica, a small 

 branch rises from the upper sac, runs almost straight down to 

 the tibia, and falls again into the main trachea just above the 

 lower sac. The remarkable sacs at the two extremities of the 

 tracheae in the tibia may also be well seen in other transparent 

 species, such, for instance, as Myrmica ruginodisov Pheidole mega^ 

 cepTiala. At the place where the upper tracheal sac contracts, there 

 is, moreover, a conical striated organ, which is situated at the back 

 of the leg. The broad base lies against the external wall of the 

 leg, and the fibres converge inwards. There are indications, 

 though somewhat indistinct, of bright rods. 



The posterior portion of the thorax is then described, and the 

 difierences which are exhibited in the presence and in the absence 

 of wings pointed out, as also the changes characteristic of the 

 sexes. The postthoracic gland, first observed by Meinert, is then 

 described ; and, lastly, the author refers to the muscles which move 

 the abdomen. 



