DAPHNIAD^E. 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 w^as 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 Daphnia?. 

 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 6tli of January she had given 

 birth to a fom-th family ; January 14th she has given birth 

 to a fifth progeny ; January 22 d 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 w^ater, the 

 most important organ producing the motion being the 

 large antennae. Such, in particular, is the manner of 

 swinnning of the I), pulex and rotunda, &c. 



Many of the Entomostraca have the faculty of returning 

 to life after having been completely dried. Schoeffer 



