188 THE FIDDLEK. 



striking obliquely upon the water, acts as an oar, with 

 tliat peculiar action which is known to boatmen as 

 . sculling. In the common Shore-crab ( Carcinus moenas) , 

 that abundant olive-green kind which on every rocky- 

 shore little boys and girls catch, by letting down into 

 the crevices a piece of string with a fragment of offal 

 tied to it, — we observe a transition condition of the 

 hind-foot ; there is a decided tendencv to an ovate 

 form, though the tip is yet taper and acute. And the 

 habits of the animal agree with this structure. The 

 power of shooting slantwise through the water exists, 

 which bears the same sort of relation to the free and 

 easy swimming of the typical Portunidce.) the Oceanic 

 Crabs of the tropics, as the long leaps of the Flying- 

 Squirrels and the Petauri bear to the sustained flight 

 of a bird. 



None of our native Crabs are " at tlie top of the 

 tree" in the swimming profession ; their efforts, even 

 those of the best of them (and there is a good deal of 

 difference in the species even of the true Portuni), are 

 awkward bunglings, when compared with the freedom 

 and fleetness of those I have seen in the Caribbean sea, 

 and among the Gulf weed, in the tropical Atlantic, 

 which shoot through the water almost like a fish, with 

 the feet on the side that happens to be the front all 

 tucked close up, and those on the opposite side 

 stretched away behind, so as to " hold no water,^^ as 

 a seaman would say, and thus offer no impediment to 

 the way. Our species are obliged to keep their pair 

 of sculls continually working while they swim ; a 

 -series of laborious efforts just sufficient to counteract 

 ^he force of gravity ; and the see-saw motion of the 



