88 A HISTORY OF RECENT CRUSTACEA 



persons wlio miglit be familiar with the smooth flat sur- 

 faces opposed to one another in the legs of a crab, and 

 who yet would never make the guess that it was an 

 arrangement to diminish friction. With the guess made 

 for them by some one else they would be contented for 

 another lifetime, and so on perhaps with the objection to 

 the guess that if friction was to be avoided, the legs would 

 not have been fringed with hairs. Fritz M tiller was well 

 aware of the old principle that Nature makes nothing in 

 vain, and was pretty confident to begin with that there 

 would not at the same point be two arrangements counter- 

 acting one another, the one increasing and the other 

 diminishinof friction. The smooth surfaces of the limbs 

 enable them to act as tight-closing lips to the breathing- 

 aperture which he discovered at their bases. As to the 

 fringing hairs Fritz Miiller hazards the conjecture that 

 they may be olfactory. This might seem a very extra- 

 vagant supposition, that a crab should have the equiva- 

 lent of a nose attached to its legs, did we not remember 

 that some crustaceans have organs of hearing in the appen- 

 dages of the tail. Moreover, Fritz Miiller observed that 

 in his Ocypode the olfactory filaments in their usual place 

 on the antennas were much reduced, and that the flagella 

 of the antenna never make the peculiar beating move- 

 ments familiar in other crabs, and he argues that in an 

 air-breathing crab, just as in the air-breathing vertebrates, 

 the sense of smell might be expected to have its organ at 

 the entrance of the breathing cavity. 



Gelaslmus, Latreille, 1818, meaning the laughable crab, 

 is a genus containing a large number of species that haunt 

 warm climates. Here, too, the orbits and eye-stalks are 

 long. The pleon in the male is narrow and distinctly 

 seven-jointed, and its base does not occupy the whole 

 width of the sternum between the walking legs. But the 

 most striking feature is the disproportionate size which in 

 the male is attained by either the right or the left 

 cheliped. 



According to de Haan his species Gelasimus arcuatus 

 is called in Japanese Siho maneld^ which means ' beckon- 



