6 



which act as scavengers, we find the sense of smell highly developed ; a good 

 example can be found in the blue bottle fly and the dung beetle. 



The organs of sight are also very keen : the structure of the eye* is very 

 insect-like : the eye of the dragon fly much resembles the eye of the crab. 



This structure of the crab's eye and his sense of smell, will, I fancy, account 

 for the fact that crabs are caught in the greatest quantities when the water is 

 muddy and thick. Crabs under these circumstances " crawl the best." Crabs 

 and lobsters also, having gone in the pots at night, will come out of them at 

 sunrise if the pots are not drawn up, because they see they are in a trap. 



Lungs of crab. The breathing apparatus of the crab is very complicated and very wonderful. 



In the case of fishes the animal has to breathe water by means of gills ; land 

 animals have to breathe the air by means of lungs ; neither of these can change 

 places without death. But the crabs and lobsters being littoral or shore 

 animals, and being liable to be left high and dry by the tide, require lungs 

 that can actually breathe both in air and water. The seal, porpoise, crocodile, 

 hippotamus, &c, though passing most of their lives in water, breathe air, and 

 have apparatus for so doing. The crab, on the contrary, breathes both air and 

 water. The lungs consist of a series of tufts of very delicate membranes 

 which are pyramidal in shape ; of these there are eight on each side. These 

 sets of eight lungs are packed away as it were in a watertight box. The 

 water therefore passes through them without interfering or coming in contact 

 with any of the other viscera. This is a most beautiful structure, not yet 

 imitated by any design of man. The inner side of this compartment consists 

 of a firm box, made of the same substance as the shell ; the outside is a 

 beautiful, delicate, elastic, expansive, membrane, and is like gold beaters' skin 

 in structure, When in good health respiration is kept up by means of a con- 

 stant stream passing through this lung-containing chamber. The water enters 

 through an aperture which I find is situated immediately under the tail. It 

 makes its exit through a slit in the neighbourhood of the mouth, where it is 

 regulated by the action of a curious valve-like structure, which is connected 

 with the mouth. But this is not all : extending along the whole length of 

 these eight finger-like lungs is a delicate curved whalebone-like filament (the 

 flabellum) lined on each side with delicate hairs, forming, in fact, a delicate 

 brush; this fits accurately on to the lungs. I find this whalebone-like 

 filament is fastened to and worked by the great door, the first of the numerous 

 doors at the crab's mouth, and which can be seen in perpetual motion, like the 

 gills of a fish when the crab is breathing. The probable use of this beautiful 

 mechanism is to keep up a gentle pressure upon the complicated lung 

 structure, and regulate the flow of water to it. There is also a valve which 

 will keep the water in the lung box, as a cork keeps the fluid in a bottle. 

 , If it were not for this structure the crab could not five equally well in the 

 water and in the air. I have reason to believe that when he leaves the water, 

 either accidentally or of his own accord, there is always a certain quantity of 

 water in the lung box, which keeps his gills moist. The bubbles proceeding 

 from the lungs of a crab or lobster when gradually dying out of water, indi- 

 cate that the air in the lung box is becoming vitiated, and a further supply 

 is required, also that the gill tufts are becoming adherent to each other, as 

 may be observed in the gills of a dead fish. These gill tufts in the crab and 

 lobster are popularly considered poison, and are called " dead men's fingers." 



Varieties of crab. It is an undoubted fact that crabs are much larger in some places than in 

 others ; the largest crabs are found on the coasts of Devon and Cornwall, 

 between the Start and the Lizard. These are sent as far as the Edinburgh 

 market. The crabs on the north-east coast of England are small crabs. The 

 north-east coast of Scotland does not produce large crabs. At Dunbar they 

 run small, and are known in the market as "Dunbar bugs." The largest 

 crabs are caught at Start Point in Devonshire. The largest Cornish crabs 

 are 11 to 12 inches across the back, and weigh from 11 to 12 pounds.f Mr. 

 Cornish of Penzance has seen a crab weighing over 12 pounds. Large 



* Crabs' eyes, as used in the Pharmacopoeia of olden times, are rounded calcareous secretions 

 found on the sides of the stomach of crayfish. These substances are supposed to act as reser- 

 voirs for the lime required by the animal to grow a new shell. They were said to be an 

 antacid, a cure for gout. At the present day a substitute for them, composed of carbonate of 

 lime, is used principally for cleaning plate. 



t Mr. Laughrin, of Polperro, says 14 to 16 lbs. 



