12 THE AQUARIAN NATURALIST. 



distance from the shore, a cargo from the clear green 

 billow. 



The element wherein the captives are kept should 

 be always sweet and quite clear; the vessels clean, 

 and free from tainted matter. Some specimens fall 

 immediate victims to putrescence ; others can resist 

 it wonderfully, either endeavouring to escape by ascent 

 or by descent, according to their peculiar nature, or 

 closing themselves up, as if to avoid its deadly in- 

 fluence. The water for most of the Crustacea should 

 be free from mud, and contain eminences whereon 

 they may rest, at will, above the surface. But muddy 

 solutions are essential to most of the bivalve Testacea, 

 and to all the Ascidian tribes ; a certain proportion of 

 mud is likewise grateful to several Amphitrites, and 

 to many Annelidans, as sand is to the various species 

 of Nereis. 



An excellent test whereby to judge of the purity 

 and wholesome condition of the water may be esta- 

 blished by the simple introduction of a few living 

 specimens of the Acorn-shell or Barnacle (Lepas), 

 which are to be found abundantly, adherent to stones 

 or shells, on any part of the coast. Whilst these 

 continue active and healthy, as testified by the ener- 

 getic display and contraction of their delicate and 

 highly sensitive arms, we may rest quite satisfied that 

 all is going on well ; but, on the other hand, their 

 inactivity ought to call attention to the condition of 

 the tank. 



The inconvenience, delay and expense attendant 

 upon the procuring of sea- water from the coast, or 

 from the ocean, Mr. Gosse soon felt to be a great 



