DUBLIN NATURAL HISTORY SOCIETY. 
39 
tempted to describe them. They consist of a number of what are ordi¬ 
narily called propagating glasses (the dealers call them pro’-glasses), six 
inches in diameter, and nine inches high ; the only thing placed in them 
besides the water is the JJlva 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 Mollusca of any kind, as 
I find them troublesome by dying 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:— 
Thia polita for four months. 
Perimela denticulata, two months, hatched zoes, and was itself 
killed and partially devoured by Thia. 
Hippolyte Cranchii, one month. 
II. pusiola , one month. 
Crangon fasciatus , three weeks; all killed by Thia. 
The varying prawn (P. varians), two months. 
Squill prawn (P. squilla), two months. 
Common shrimp ( C. vulgaris), three weeks. 
Hippolyte varians, three months. 
Most of them died merely through neglect in changing the water, 
which I generally do not oftener than once a month. The tank is kept 
in a shady place, and uncovered, and the animals are but seldom fed, 
and then as often on small snails or woodlice as anything else. The 
sea water for change is kept in a large bottle, with a narrow neck, and 
transparent sides, closely corked, and sometimes, when used, has been 
three months or upwards in the bottle; so that the keeping of marine 
animals of the crustacean group is not such a difficult task as is com¬ 
monly supposed, 
The zoes differ from those of Cancer pagurus in having no lateral or 
frontal spines on the carapace; in having no spines at the inner angle 
of each joint of the abdomen below. The carapace is also very large; 
the abdomen is divided into six rings; the thoracic limbs are three (?), 
the most anterior hardly to be distinguished in form from the ex¬ 
ternal foot-jaw of many of the Porcellanidae. 
A discussion arose regarding the practicability of growing Algae in 
vivaria without a point of attachment. Professor Kinahan stated that 
TJlva lactuca and JEnteromorpha intestinalis both do well thus, but that 
he had found the latter Algae, even when attached, a bad tank plant, 
as it is very apt to become yellow. He could not speak of any 
other species, as he found them to answer so well that there was no ne¬ 
cessity for change; the brown weeds he had found were nearly certain 
destruction to many of the Crustacea. 
