OUR FRESHWATER ENTOMOSTRACA. 
49 
water-fleas as in the daphnise. The new shell or covering 
having grown under the old one, when the process of changing 
it commences, the insect fastens itself to the bottom or side of 
the vessel in which it is, or to any solid object near it, so as to 
give itself support ; then, by moving its limbs and shaking the 
valves of the shell, it loosens the old covering, and in a short 
time frees itself from it altogether. 
The fertility of these water-fleas is enormous ; specimens of 
the Cyclops quadricornis are often found carrying thirty or forty 
eggs on each side. One female has been seen to lay ten times 
successively, and one access of the male suffices to fecundate the 
female for life. Jurine has watched the hatching of the eggs 
and the increase of this little creature with great care, and has 
given us a calculation by which we may easily ascertain the 
amazing fertility of the species. He supposes, to be within 
bounds, that the female lays eight times within three months, 
and each time only forty eggs. At the end of one year this 
female would have been the progenitor of 4,442,189,120 young! 
To counterbalance this amazing fertility, they have many 
enemies ; and both young and old are devoured in vast numbers 
by various aquatic animals that exist in the same ponds and 
ditches in which they reside, as well as by the cattle that come 
to drink these waters. 
The number of species of the family Cyclopidce , described as 
living in the fresh waters of Great Britain, are few, amounting 
to only five or six ; the greater number being natives of salt 
water. 
Such are the leading facts and details of the development and 
history of the greater portion of our freshwater Entomostraca. 
The two species we have selected are amongst the most common 
of all our shell-insects, are to be found in all our stagnant pools, 
ponds, and ditches, and may be easily procured and preserved 
by any person who would wish to cultivate a further aquaintance 
with the group to which they belong. 
Many other and very beautiful species, however, are almost 
equally worthy of the reader’s attention. Let us, for instance, 
take a stroll as far as Blackheath. On that most delightful of 
the “ lungs of London,” we find many pools and little ponds of 
water, some of which are dried up during the heat of summer 
and filled again in autumn, when heavy rain has fallen. We 
will select this one among the gravel-pits near the gates leading 
to Greenwich Park, and, throwing in our hand-net, bring it to 
the brink, and wash it into our little basin. An extraordinary 
sight is thus brought before us. Thousands of fine large daph- 
nise, of two or three kinds, two or three species of lynceus and 
cyclops, and myriads of the little bivalve shell-insect called 
cypris, swim rapidly in the water. Conspicuous, however, 
