78 DUBLIN NATURAL HI8T0ET SOCIETY. 



is most active, running over the sides and bottom of the tank after the 

 lights are extinguished, the noise it makes being considerable as it 

 rattles over the glass. Its mode of feeding is sometimes most amusing. 

 On its back, completely concealing it, is a large mass of sponge, which 

 of course the crab carries about with it everywhere ; it, however, causes 

 these strange passengers to pay toll occasionally, as frequently I have 

 seen the E. aspera stretching its long anterior limbs backwards over its 

 carapace, and, deliberately tearing off a portion of the sponge, coolly 

 proceed to tuck it in between its jaws ; sometimes holding the piece of 

 sponge in one of the chelae, it daintily tears off small pieces from the 

 mass, which it then quietly devours. I detected it once feasting on a 

 little varying Hippolyte, 11. varians, which was in the same tank ; but 

 generally speaking, its food must consist of the Entomostraca and other 

 minute animals, &c., which abound in the water, and possibly also the 

 Ulva. It is a most sluggish animal, slow and deliberate in its move- 

 ments, and during the day remains with its back to the light in a lair 

 it has formed under a projecting piece of Ulva lactuca, its long and 

 beautifully carved arms kept semiflexed at some distance from each side of 

 its body ; and the whole animal perfectly motionless, except an occasional 

 vibration of the foot-jaws, looking like some monster in his den. The 

 species is not uncommon in moderately deep water on the banks around 

 the coast, and I would recommend it as a good species to those who keep 

 tanks, as it is generally tenacious of life, and bears travelling well, living 

 for a long time, even in a small quantity of water. 



My tanks, in which I have succeeded in keeping many of the rarer 

 Crustacea, are so convenient, and their arrangement so simple, that I am 

 tempted to describe them. They consist of a number of what are ordi- 

 narily called propagating glasses (the dealers caU them pro' -glasses), six 

 inches in diameter, and nine inches high ; the only thing placed in them 

 besides the water is the Ulva lactuca, selecting a broad piece unattached 

 to stones, as I find that stones harbour dirt ; the seaweed must be a 

 large piece, as one of its chief intentions is to afford cover and shelter 

 to the animals from the light. It requires to be occasionally renewed, 

 as the animals feed on it. I seldom introduce MoUusca of any kind, as 

 I find them troublesome by djdng at unexpected times, and thus poi- 

 soning the tank, and I have never seen any occasion for their services 

 in keeping my tanks either clean or healthy. 



In this same tank I have had at various times, under the above 

 conditions, the following rare Crustacea ; — 



Thta polita for four months. 



Perimela denticulata, two months, hatched zoes, and was itself 

 killed and partially devoured by Thia. 



Hippolyte Cranchii, one month. 



H. pmiola, one month. 



Crangon fasciatm, three weeks ; all killed by Thia. 



The varying prawTi (P. varians), two months. 



SquiU prawn (P. squilla), two months. 



Common shrimp ( C. vulgaris), three weeks. 



Hippolyte varians, three months. 



