CRUSTACEANS 



although that is not extruded when the rest of the apparel is thrown off. 

 On the other hand, it would be wrong to regard the operation as 

 universally simple, as the facile casting of old clouts, to find a fairer and 

 better fitting costume beneath them. There is often no such ground 

 for evoking envy in the impecunious children of men. In all species 

 armed with massive nippers the withdrawal of big muscles through 

 narrow articulations is a hazardous and probably painful operation. Nor 

 can it be said without reserve that, prior to the moult, ' the constituents 

 of a new shell are deposited between the body and the old shell.' The 

 discarding of the latter exposes indeed the new coat that lay beneath it, 

 but the fresh vesture is unfinished, not yet properly calcified. This is a 

 necessary condition of the whole procedure. The muscles first of all 

 become flaccid for purposes of extraction. They then assume a certain 

 rigidity. Finally they expand to that fuller capacity which made a 

 change in the exoskeleton essential. When the coat is once well hardened 

 by calcareous salts such expansion is no longer possible. In the meantime 

 the crustacean without a solid crust is exposed to anxiety and peril. 

 Another incident in the biology of these creatures may at the first glance 

 be thought rather enviable. Wolves and Spartans have been known to 

 escape from fetters, and less heroic individuals can avoid the pain and 

 danger of wounded limbs, by artificial amputation. But the tribe of 

 crabs and lobsters are provided by Nature herself with a special groove 

 at which they can easily throw off almost the whole of an inconvenient 

 leg. Also from the stump they can grow a new limb. But ' Observer ' 

 exaggerates their good fortune in affirming that the loss of a claw is not 

 a serious matter, and that its restoration may be counted on as speedy. 

 On the contrary, the repair of appendages is slowly accomplished, perhaps 

 requiring several exuviations for its completion, and in any case leaving 

 an interval during which the cripple must be at a grave disadvantage 

 among its fully-equipped competitors. 



Our river crayfish and our common lobster, alike as they are in 

 general appearance, belong in fact to two different though nearly allied 

 families, respectively the Potamobiidas and the Nephropsida?. Into all 

 the distinctions between these two it is unnecessary here to enter ; but, as 

 an example of them, it may be mentioned that in the former family the 

 segment that precedes the flexible tail is partially free, whereas in the 

 lobster it is firmly adherent to the other segments covered by the 

 carapace. 



Crayfishes are tolerably tenacious of life, and can be to a certain 

 extent domesticated. By the kindness of Mr. Machin and his sister I 

 was put in communication with Mr. and Mrs. Eddison, of Shireoaks 

 Hall, near Worksop, with the result that Mr. George Eddison wrote to 

 me from that residence on 16 August, 1903, as follows : 'The crayfish 

 I have pleasure in sending you by to-night's post have been caught this 

 afternoon in the cascade which runs from one pond to another in the park 

 here. I have known crayfish to be in these waters for over fifty years, 

 where they breed. These are of average size.' The specimens packed 



