History of British Entomostraca. 4 1 1 



veral ephippia from the same saucer, and isolated them in the same 

 manner. December 5th, three young ones born. 6th, two more. 

 8th, two more. 10th, two more. 16th, one more. 



On the 19th November I isolated a Daphnia with the ephippium 

 attached. 21st, it has thrown off ephippium. December 5th, one 

 young one born from the ephippial eggs. I have repeatedly per- 

 formed the same experiment, and have always found the same re- 

 sults. The young from these ephippial ova do not differ from those 

 born naturally, unless that perhaps they are a little longer in com- 

 ing to maturity. In a young Daphnia pulex born naturally on the 

 8th December, it moulted the first time on the 12th, or four days 

 after birth ; fourth time and had eggs, on the 21st, or thirteen days 

 after birth .; whilst in a young one of the same species born from an 

 ephippial egg on the 5th of December, the first moulting was not 

 till the 13th, or seven days afterbirth, and the fourth when she first 

 had eggs, not till the 3d of January, or twenty-nine days after birth. 

 The periods between each moulting are also longer than in the others. 

 It has been asserted, as I have mentioned above, by Jurine, that 

 these ephippia are the consequences of a disease these insects are 

 subject to, and that they have the effect of arresting their future fe- 

 cundity. From the experiments which I have detailed above, and 

 which I have mentioned as having been also made previously by 

 Straus, it is evident that they are not a disease, and that instead 

 they are 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 them 

 as arresting the future fecundity of the insects. On the 29th 

 of December, I isolated two of Daphnia 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 correspond- 

 ing to its figure, and a scar or deeper mark like a cicatrix where the 

 ampullae containing the ova were situated. 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 their matrix ; and on the 

 8th the first family were born. Watched the farther progress of 

 one of these Daphniae. On the 1 6th 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 gave birth to a third fa- 

 mily. On the 6th January has given birth to a fourth family. Ja- 

 nuary 14th, has given birth a to fifth family. January 22d, has given 



