BY W. R. COLLEDGE. 55 
but in the morning, and towards evening, likewise on 
cloudy days, they may be found near the surface. I have 
noticed that frequently a little air finds admission beneath 
the shell in some instances, and they seem to lie in conse- 
quence helpless on the surface of the water. The outer 
carapace covers the whole head and body in one piece. 
It is thin and transparent, of a reticulated structure. the 
cells being square, and occasionally, of oblong forms. It is 
open frentally from the base of the second antennze down 
to near the origin of the shell spine. Within this. is a 
second shell free over the abdomen, united dorsally, and 
lining the whole of the cephalic portion. It is denser 
than the outer coat, and is dotted with stellate and irregular 
marks. It contains’on the pleura the convoluted shell 
gland. On turning the flaps of these two coats back, there 
is seen the branchial feet. These consist of five pairs ranged 
on each side of the abdomen. The first, second and fifth 
differ from each other, but the third and fourth are some- 
what similar in structure. The muscular portion is formed 
like an elongated plate, while from the outer edge droops a 
deep fringe of closely set setce. In the third and fourth 
pairs there are nearly a hundred lying side by side in one 
foot, all set at a regular distance from each other. Under 
a high magnification, each proves to be a delicate feather, 
so airy and perfect as though it belonged to some fairy 
world, such as Shakespeare imagined in his dreams. Each 
edge of these dainty elfin feathers slightly overlaps its 
neighbour, thus presenting a close network to the water. 
At their base the filaments are united each to its neighbour. 
Ceaselessly do they move with a graceful rhythmic move- 
ment. An essential part of their work is to supply the 
respiratory pouches with fresb currents of water, but a 
no less important function they have is in procuring food. 
The continual motion creates a current, which sets in 
towards the body. 
Vegetable spores. volvoces and other minute organisms, 
which serve as food, are borne along by it. The water 
filtering through the fine network leaves the residue beneath 
the first and second pairs of feet. If the mass is too large, 
or not good for food, then the tail-piece. armed with its 
two pectinated claws, is drawn in between the two rows 
