176 THE ZOOLOGIST. 



evolution. They are comical creatures at first, these zoea, but 

 each moult makes them more and more like the adult Prawn. 

 Only a small percentage survive to maturity out of the number 

 of ova there are at first. 



Palcemon varians is the easiest of all the Prawns to keep in 

 captivity. It does not trouble much about the density of the 

 water, and if the aquarium be properly made up can take care of 

 itself during its owner's absence from home. I have left these 

 Prawns for a month or more, and found them all right on my 

 return home. I am not sure they do not sometimes eat sea- 

 weed ; they certainly love to pick the laver about with their 

 pincers. They are the only Prawns I suspect of occasional 

 vegetarianism. I have seen them holding a piece of the green 

 lettuce laver in their pincers, just as if about to put it into their 

 mouths. As they seem none the worse for being left for weeks, 

 they must either eat seaweed or have the power of enduring long 

 fasts. 



It is curious how Prawns lose their transparency when they 

 are unwell or dying, and how opaque these crystal creatures are 

 when dead. I can always see if they are ailing or distressed at 

 all by noticing whether they are quite clearly transparent or 

 otherwise, and generally in time to save their lives. I mostly 

 lose them either by a sudden frost or by their fighting with one 

 another. Some of the large Prawns are very fierce and pug- 

 nacious, especially the females when they are carrying ova. 

 One of these contrived to kill a Hermit-Crab in the same 

 aquarium, and another one, in with a Goby, killed the fish. I 

 like to keep them with the fish, as they pick up all tiny morsels 

 of meat these and the Hermit-Crabs reject. With scraped meat 

 there is sure to be some not eaten, and if left it will foul 

 the water ; Hermit-Crabs are especially wasteful of meat given 

 them. 



The regulation food for my Prawns is scraped beef. This 

 they take off a pointed wooden skewer, and evidently know where 

 their food comes from, as they are eagerly alert at sight of the 

 skewer. At other times they endeavour to arrest my attention 

 by coming to the front of the aquarium and palpably begging for 

 food. 



Crangon vulgaris. — I have had such success with the Common 



