27 
mentioned on account of their rarity, but representatives of the 
species I have indicated would form a splendid collection. 
* * * * Having given so much attention to the Actinia, 
it is time to specify some other objects which may give additional 
interest to the aquarium. 
Some of the smaller zoophytes and polyzoa ( ‘especially Sertu- 
laria, Plumularia and Flustra) may be added for the beauty of 
their polypary or zoarium, 
A common starfish or two (of small size) may be introduced, 
but they will require to be watched. The most hardy of the 
Asteriade is ‘‘ The gibbons Starlet” (Asterina gibbosa). I do not 
recommend any of the ‘“‘ Brittle stars,” ‘‘ Egg-urchins,” or ‘‘ Sea- 
cucumbers.”’ : 
Of annelids, Serpula triquetra (hardy) S. contortuplicata 
(more showy but less hardy) Sabella tubularia and Terebella conchi- 
lega are worth trying. The Serpule have calcareous tubes; 
Sabelle construct their tubes of grains of mud and sand; Tere- 
belle, of small stones and broken shells. 
A small oyster is useful in assisting to preserve the clearness 
of the water, but the shell must be hard and clean, quite free 
from worm holes and the burrowing sponges. 
Cockles are unsafe. A mussel if very young when put into 
the tank, may live some time. A few periwinkles are useful, 
natural and safe additions, but other molluses, including the lovely 
sea-slugs Doris Folis, &c., had better be eschewed. 
Crustacea should not be admitted into an aquarium devoted 
principally to zoophytes. Crabs, if large, disturb the anemones, 
and eat up the larval forms of life which should be allowed to 
mature ; while, if small, they are in danger of being eaten, but 
only partially digested, by the actine. The latter objections apply 
equally to shrimps and prawns, which are pretty objects while 
swimming clear of the tentacles of their natural enemies. The 
same remark is applicable to small fishes, while large ones cannot 
be kept alive unless in a tank devoted principally to them. For 
such an aquarium the Gobies, the Blennies and small Grey Mullet 
are the most suitable. Although the tank may (as it should 
always) be kept covered, there will still be some loss by evapora- 
tion which in time will sensibly increase the density of the water. 
This may be ascertained by density-balls indicating a specific 
gravity of 1.026”, or, better still, by the hydrometer. “Any serious 
variation from the standard must be rectified by the gradual addition 
of water, either distilled, or pure common water that has been 
boiled, 
