306 The Entomostraca of Mid-Lothian. [Sess. 
chitinous covering which, although widely different from the 
shell of a mollusc, may still be popularly called shell. These 
rings are united by a strong pliable membrane. The creatures 
are extremely active, swimming in a quick succession of jerks 
or darts, produced by vigorous strokes of the antennas and feet. 
Some of them, as the Cyclops, keep a fairly straight line when 
swimming; others, as the Canthocamptus, move alternately to 
right and left. It is often possible to recognize from the 
method of swimming to what genus, or at least what family, 
a specimen belongs; and in some cases even the species itself 
can be recognized by its peculiar method of progression. This 
is the case with Cyclops phaleratus; being a very flattened 
species, it is able to preserve its balance easily and to crawl 
on the surface of the mud, or on the sides of the vessel in 
which it is placed. We have frequently taken specimens of 
C. phaleratus from a gathering, and put them temporarily in a 
few drops of water in a watch-glass, meaning to examine them 
later on. After leaving them ten minutes or so, and return- 
ing, it has been quite a common experience to find that one or 
two have crawled right out of the watch-glass, and are wander- 
ing on the underside of it, or on the table. 
The copepods generally swim with the ventral surface 
downwards, but we have often seen some species of Cyclops 
swimming, so to say, wrong way up—with the dorsal surface 
downwards. 
The Cyclops is peculiarly liable to parasites, both animal 
and vegetable; we have often seen brilliant green specimens, 
which owed their colour to the presence of numbers of minute 
unicellular algas growing on them; and others we have seen 
swimming about surrounded by a white cloudy-looking mass, 
which under the microscope proves to be sometimes hun- 
dreds of bell animalcules. On the Canthocamptus there may 
generally be found a few specimens of a small animal parasite 
—an infusorian living in a delicate hyaline cup. These so- 
called parasites do not prey on their host, but merely attach 
themselves to its shell and reap the advantage of being con- 
—— 
stantly carried about to fresh food-supplies; but when present . 
in large numbers they must cause it serious inconvenience. 
Turning to the ostracods, it seems hard at first sight to 
ascertain anything more than the mere outline and colour of 
