24:Z THE CAUSES WHICH PROPAGATE 



inclined lateral walls, wliicli correspond, and are o^ently concave. 

 With either lateral wall of the bladder the tympana stand in 

 closest contact, isolating- the anterior portion of the tibia where 

 is the boat-shaped excavation. 



With the large tracheal tubes of the fore-feet pass down two 

 nerve-threads of dissimilar thickness. The thicker lies posterior 

 to the trachea, ramifies in the upper leg, and inferiorly beneath 

 the large air-bladder. The thinner behaves somewhat similarly, 

 but differs inasmuch as it sends a branch direct to the boat- 

 shaped excavation of the air-bladder, that widens just above into 

 a fiat ganglion [n], whose uuder-end enters the boat-shaped 

 excavation in the form of a band, attaches itself at the inferior 

 part, and terminates. Covered above with a whitish pigment, 

 this ganglion contains numerous oval granular bodies, appa- 

 rently the nuclei of g-lobular cells, between which are numerous 

 little rods, or pear-shaped bodies, similar to those in the acoustic 

 g'anglion of the grasshoppers. Its posterior superficies tan- 

 gential to the bladder is smooth, the anterior wavy, a feature 

 owing to a line of thirty or forty contiguous transparent vesicles, 

 each containing a small pyriform nucleated mass, probably 

 the anterior termination of nervous threads. 



Von Siebold, in conclusion, observes the suitability of the 

 tracheal pipes for the function of a eustachian tube in respect 

 of the drumskin ; the division of the latter into a posterior 

 thin membrane and anterior chitineous thickening analogrous to 

 what we find in the grasshoppers, as also the similar structure 

 of the acoustic or MuUerian ganglion, which appears likewise to 

 contain a watery fluid. We also have here a more or less com- 

 plicated external ear. Von Siebold recognises auricles similar 

 to those of the Leaf Crickets in the House and Field Crickets. 

 In these there is apparently bat one effective tympanum on 

 each foreleg, placed at the outer side, instead of two, as we find 

 in the Leaf Crickets. This is certainly the case with the House 

 Cricket, where we find only one opening; but in a kindred sort, 

 G. ac/iatimis, there also exists an orifice on the inner side, similar 

 to that on the outer but smaller, and in the Field Cricket a 

 small round opening closed with a membrane, presenting us, 

 we surmise, with the rudiments of a drum. 



From Dr. Vitis Graber we o-ather that certain Locustida) and 



