DAPHNIADJE. 
87 
disease these animals are subject to, and that they have the 
effect of arresting their future fecundity. From the ex- 
periments I have detailed above, and from similar ones 
made previously by Straus, it is evident that they are not 
a disease, and that instead of being so, they contain ova 
of a particular nature, destined to outlive the severity of 
the winter, and to perpetuate the species, which would 
otherwise perish altogether. From some experiments 
which I instituted upon this subject, I also found that 
Jurine is wrong in asserting that they arrest the future 
fecundity of these little creatures. 
On the 29th December I isolated two specimens of 
D. pulex, with their ephippia attached. On the 30th 
both had thrown off their ephippia, and both had moulted. 
Upon close examination, I found that on the shell where 
the ephippia were situated, there was left a mark corre- 
sponding to its figure, and a scar or deeper mark was 
visible where the ampulla containing the ova had been. 
In the ovaries were to be seen the transparent globules or 
first appearance of the ova. On the 4th December both 
had eggs lodged in the matrix, and on the 8th the first 
family were born. 
I watched the further progress of one of these Daphniae. 
On the 16th December she had given birth to a second 
family, but did not moult till the 20th, when she again 
had eggs in her matrix ; and on the 24th she gave birth 
to a third family. On the 6th of January she had given 
birth to a fourth family ; January 14th she has given birth 
to a fifth progeny • January 22d she has had a sixth family. 
One or two other experiments, with similar results, prove 
satisfactorily that the assertion of Jurine is incorrect. 
The motion of most of the species belonging to this 
family is chiefly by short bounds through the water, the 
most important organ producing the motion being the 
large antennae. Such, in particular, is the manner of 
swimming of the D. pulex and rotunda , &c. 
Many of the Entomostraca have the faculty of returning 
to life after having been completely dried. SchcefFer 
