35 



am by no means sure, and I slmnld not be suiprised to find that 

 hundreds are still living, having discovered some food for them- 

 selves. 



The change from a Zoca to a Crab is not effected per saltim but 

 m the next stage, which may be in some respects likened to the 

 pupa state of Insects, the Zoea becomes a creature bearino- a con- 

 siderable resemblance to a Lobster, or Crayfish; that is°to say 

 like those Crustacea it has a long tail ; it is, however, more like a 

 species of Crab exhibited in the tanks of this Aquarium, called a 

 Galathea." 



In this state the young Crab was known to Naturalists as 

 a distinct genus, under the name of Megalopa. 



The Megalopa changes into a Crab,°the first change, however 

 not being quite the perfect form, which is attained in the fourth 

 change. 



After the last change the Crab is about the eiglith-of-an-inch 

 long, with a hard shell ; it grows to the utmost contents of the 

 shell and as the shell is non-elastic, growth would be stopped but 

 for the power the Crab has of casting its shell ; this is one of the 

 most wondei-ful facts in nature. 



I have, myself, had numerous Crabs which have come out of 

 their shells, molting both the exterior as well as the interior 

 parts, the whole being cast together and remaining entire, so that 

 I was constantly deceived into the impression that one of my 

 Crabs had died. ^ 



Several molts take place before a Crab reaches its full size • it 

 may be known whether it is quite mature by the fact that when 

 the shell has remained immolted for some time it becomes covered 

 with barnacles, and in some cases Sea Weeds and Po1vzo£e this 

 shows that the final size has been reached. 



The changes from a Zoea to Crab are more marked than from 

 a Zoea to a Lobster or Prawn, but they are similar in kind, and a 

 metamorphosis may be said to exist in a greater or less degree 

 throughout the Class Crustacea, being most marked, as might be 

 expected, m the highest foi-ms, and least in the lowest 



The highest forms, indeed, such as "Crabs," dm-ing their meta- 

 morphosis pass through stages closely resembling the perfect state 

 of ower forms. The Zoea state of the Crayfish, Palinurus, so 

 ately as 1855, was described and figured as a new species, under 

 he name Phyllosoma, but Mr. Lloyd bred it at Hamburg, in 

 1866, and proved it was a Zoea. 



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