LINNEAN SOCIETY OF LONDON. 1 5 



to frighten ine away from my purpose by making this particular 

 sound. It is not necessary- to dwell longer on this mechanism, 

 which has so close a resemblance to that which we ourselves use 

 in many acts of life. 



I will now pass on to speak of a different contrivance present 

 in certain Crustacea, producing a sort of creaking sound, which is 

 made by what is known as a stridulating-, or creaking-apparatus. 

 Perhaps, on the whole, the simplest form of this stridulating- or 

 creaking-apparatus is that met with in a common tropical crab 

 known as Matuta picta. The upper border of the propodite of both 

 chela? has .two file-like surfaces which can be rubbed against the 

 carapace, producing a creaking sound very much of the same 

 character as would be caused if a piece of iron held in a vice 

 were filed. We have here, then, a very simple form of stridu- 

 latiug-apparatus in this Matuta. A somewhat more complex 

 one is met with in a tropical crab which is known as Ocypoda 

 ceratophthahna. This crab has a very square carapace, and the 

 eye-stalks are prolonged beyond the eye itself. Sometimes the 

 left chela, sometimes the right, is very large, and has a curious 

 ridge, which extends from above downwards on the surface of 

 the propodite nearest the carapace, provided with a most regular 

 and beautiful set of file-like teeth. The upper portion of the 

 ridge is provided with coarse teeth, but in the lower portion 

 we find that the teeth are very much finer. In this case we 

 probably have a stridulating-apparatus which is capable of 

 giving out two different kinds of sound. It is probable that 

 the coarser toothed region will give out a deeper note than the 

 finer region. It is hardly likely that the same note would be 

 produced, because I take it that these stridulating-organs are to 

 be compared, as regards the mechanism of sound-production, 

 rather to a Savart wheel than to any other sound-producing 

 organ ; that is to say, the resultant note is determined by the 

 number of blows given by these teeth, and will depend then upon 

 the rapidity with which the toothed surface is drawn over some 

 other part of the body, and also on the number of teeth upon 

 that surface. 



There is one still more perfect stridulating-organ in the 

 Crustacea, which, though not presenting the complexity that we 

 see in the case of the Ocypoda, yet offers a very curious pro- 

 blem, of which I can give no solution, and I shall be very glad 

 if any of the Fellows here can throw light on the subject. In 

 the case of a very common crustacean indeed — the common spiny 

 lobster (Falimirus vulgaris), familiar to most of us as so often 

 displayed on our fish-stalls, — this spiny lobster has a very com- 

 plex organ for the production of sound. Those who have been 

 around our Cornish coast and have seen the large store-boxes in 

 which these and other Crustacea are kept until they are required 

 for the market, may have noticed, when these store-boxes are 

 brought out in order to yield up their contents for sale, a creak- 

 ing sound like a colony of frogs croaking. This croaking sound 

 is produced by the great antenna; of this Palinurus vulffar/n 



