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inner and upper borders with file-like surfaces which produce the sound by 

 rubbing against the smooth parts above referred to. 



Towards evening, whilst walking on the headland, he found that there were 

 a great many of the large green grasshoppers (Acrida viridissima) in the 

 tamarisk trees all around, and that they were making the air quite 

 lively with their peculiarly loud, shrill, and continuous noise. [A drawing 

 of the insect having been made upon the black-board, Professor Stewart 

 proceeded to explain that at the base of the wing on one side there was a 

 kind of ridge which had a serrated edge somewhat like a file.] This dentate 

 ridge was the "fiddle-bow " which was the chief factor in the production of 

 the noise. On the opposite portion of the other wing there was also to be 

 found a very clearly-defined circular space covered by a delicate membrane, 

 and it was by the rubbing of the bow across the hard ridges near this that the 

 sound was produced. Of course it would be of no use for the creature to be 

 able to make a noise unless that noise could be appreciated by its fellows, and 

 so it might be fairly assumed that if any animal had a special apparatus for 

 making a noise it would also be provided with a special apparatus for hear- 

 ing it. Such an organ was found to exist just below the knee of the fore- 

 leg. Now, though at first sight it might seem to be peculiar, yet it would 

 be seen that after all this was not by any means a bad place for an auditory 

 apparatus under the circumstances, because, as this insect, unlike the other 

 grasshoppers, made a continuous sound, it would be very inconvenient if 

 the organ of hearing was situated near to that which produced so much 

 noise. Clearly, then, this position was well removed from the source of 

 sound. On further examination it was found that in the po'sition indi- 

 cated there were two slit-like holes, each leading to a cavity, within 

 which was found a kind of tympanic membrane connected by a nerve 

 which could be traced as coming from the first thoracic ganglia. [The 

 special and peculiar form of the nerve terminations was also drawn upon 

 the board.] In the case of the common brown grasshopper the conditions 

 were somewhat different, for, instead of a long-sustained noise, the creature 

 uttered a series of short, sharp chirps, with a very clear interval between 

 them, and therefore they might expect that the mechanism of its audition 

 would be adapted to the circumstances. The sound was produced by rubbing 

 the inner aspect of the femur of the hind leg upon the edge of the elytron, 

 and there was found upon the first segment of the abdomen a small semi- 

 lunar slit, which led into a little chamber. Inside this was a horny ridge, 

 which occupied nearly half its diameter, and a very thin membrane was 

 stretched across this, so that it very much resembled the top of a tam- 

 bourine. It had been thought that this was an organ for increasing the 

 resonance of the sound, though he inclined to the belief that it was not a 

 sound-producer, and he agreed with those who thought that it was rather an 

 organ of hearing. But, whatever it might be, it was certain that the noise 

 made was intermittent, and that the organ was perfectly in the position for 

 hearing to advantage. Examination showed that from the last thoracic 

 ganglion a nerve ran directly to this part, a fact which went far to show 

 that the arrangement might be an auditory apparatus. 



