4372 Marine Aquarium. 



The delicate bright green sea- weeds of the Ulva tribe seem to be the 

 most suitable ; those in the jar now appear as fresh as when intro- 

 duced. The red kinds that I have tried, though making a beautiful 

 appearance while fresh, soon become sickly and lose their colour. 

 The plants now in use were placed in the vessel just as they were 

 torn from the rock, without any portion of their solid support being 

 removed with them. Into this receptacle were introduced small fish, 

 Crustacea, Mollusca, and Zoophytes. The fish were three specimens 

 of the smooth shan, tried at different times, but not one survived 

 twenty-four hours, which rather surprised me, as on one occasion 

 1 succeeded in keeping a specimen alive for more than half a year in 

 a tumbler, as recorded in a former number of the ' Zoologist.' 

 Among the Crustacea were some sand-shrimps, but they too appeared 

 out of their element, and always died in a few days, or fell a prey to 

 their stronger comrades, the crabs, on whom confinement seems to 

 have no other effect than to increase their naturally crabbed dis- 

 position, and foster a spirit of exclusiveness, which resents the intru- 

 sion of almost any living thing as an infringement of their rights and 

 privileges. One specimen of the common kind has ruled in the viva- 

 rium with iron sway for the last three months, and woe to any of the 

 weaker brethren that do not get speedily out of his way. I once intro- 

 duced a full-grown specimen of the porcelain crab (Porcellana platy- 

 cheles), thinking that the large forceps and remarkable pinching 

 powers of this species would compensate for its inferior weight to this 

 doughty champion, but the next morning found my old friend quietly 

 discussing a claw of his luckless victim, whose severed limbs orna- 

 mented the bottom of the jar. On the 27th of February I found 

 a marine worm, with numerous legs (I believe a Nereis), among the 

 rocks, and placed it in the vessel ; two days after I discovered several 

 fragments of it in the jar, consisting of four or five segments each, 

 which had been cut asunder by the trenchant nippers of the afore- 

 mentioned crab. On fishing out one of these portions, I was surprised 

 to see it exhibiting strong motion, protruding and retracting the legs 

 with considerable vigour. I placed it under the microscope, the better 

 to observe the movement, at 10 minutes after 1 o'clock, and at 

 25 minutes after 2, when I went out, the motion still continued, but it 

 had ceased on my return, at J past 4. How long the segments had 

 been severed, when first observed, it is impossible to say, but the 

 movement was vigorous during the hour and a quarter that it was 

 under observation. Among the Mollusca specimens, various common 

 univalves were at different times introduced, and would flourish for 



