The Zoologist — February, 1874. 3847 



well confess that in addition to whatever humane feelings I had in 

 thus saving these animals' lives, and also in seeing whether they 

 would breed under the circumstances stated, there was in the act a 

 little of a spirit of mischief, to see whether British naturalists would 

 squabble at the appearance of living animals so essentially non- 

 European if they turned up in England, and whether, if so, and by 

 what rule, they would be admitted to the British Fauna; and I am 

 rather disappointed at finding there has been no more "fending 

 and proving" than there has been over the matter. 



It is interesting to go into the reason why these and some other 

 lungless aquatic animals are brought from great distances alive and 

 well, and with ease, while so many other lowly-organized lungless 

 water animals are transported with such great difficulty. We apply 

 the term "hardy" to such crabs as Limulus ; to the Old and New 

 World land-crab {Gecarcinus) ; to the West Indian land hermit- 

 crab [Cenohita) ; to Sesarma, a crab (allied to our English Gono- 

 plax) from the Navigator Islands; to our British shore-crab [Car- 

 cinus) ; and to some others, but I name only these five as being 

 those with which I am acquainted in a living state; and by 

 "hardy" we undefinedly mean that these animals are constructed 

 to live for long periods when they are not actually immersed in 

 water, but where they can obtain enough water to keep their gills 

 moist enough for the sufficient aeration of the blood coursing 

 through their gill-filaments; and in accordance with this arrange- 

 ment all of these five are eminently shore animals. 



We are now beginning to learn that, up to a certain point, the 

 value of water for non-lung-breathing aquatic animals does not so 

 much depend on its amount as upon its distribution in such manner 

 that it shall absorb the greatest quantity of atmospheric air, or 

 rather of the oxygen which enters into the composition of that air, 

 leaving much of the nitrogen out, unabsorbed. The earliest 

 observer known to me of this fact was the late Dr. R. Ball, who, 

 in Bell's 'British Crustacea' (8vo, 1851), records how much better 

 he kept a crayfish {Astacus) in a shallow vessel than in a deep 

 one. In all my aquarium work I keep this law in view, and I 

 regulate the amount of surface of water exposed to air, as well 

 as the actual quantity of water, according to the known requn-e- 

 ments of the animals to be kept; and the result is very surprising 

 both on the health of the creatures, and in the saving of the 

 money cost of constructing and maintaining aquaria. I also 



