406 History of British Entomostraca. 



thors had never seen the males, nor ever witnessed the act of copu- 

 hitlon. Muller and others^ however, detected the male, and witnessed 

 the act ; and it is ascertained that one single copulation is sufficient 

 not only to fecundate the mother for her life, but all her female de- 

 scendants for several successive generations. This was observed by 

 SchoefFer, who followed them up to the fourth, by Straus to the fifth, 

 and Jurine tothesixth, — the latter observing, that he thinks it probable 

 it might extend in some species to the fifteenth generation. Ex- 

 traordinary as this may appear, I have further found that the young 

 produced from the ephippia are also fecundated by this one copu- 

 lation, and have progeny ; and that their young again also produce 

 eggs, without the intervention of the male. I have followed up the 

 successive generations as far as the fourth in the Daphniae born 

 in the usual manner ; and as far as the third in those born from 

 ephippial eggs, and have found from repeated experiments that those 

 Daphniae which had ephippia became loaded with eggs soon after 

 they had thrown off their ephippia, and had progeny again without 

 the intervention of males ; and that the young so born from those 

 Daphniae, which had thrown off the ephippia, and become pregnant, 

 were also independent of the access of the male, and became mothers 

 in the same manner as the young of other Daphniae. November 

 29, Isolated a D. piilex, with an ephippium. 30th, Ephippium 

 thrown off. December 4, Daphnia has eggs. 8th, young ones 

 born. 9th, has eggs again. 16th, young ones born. 20th, has 

 eggs again. 24th, young born. 25th, has eggs again. January 

 6, young born. Mother has eggs again. 14th, young born. Mo- 

 ther again has eggs. 22d, young born. February 1, has eggs 

 again. 8th, young born. On the 8th of December, isolated one 

 of the young born from the subject of last series of observations, on 

 the 30th November. 21st, has eggs. 28th, young born. 29th, 

 has again eggs. January 9, young born. Mother has eggs again. 

 24th, young born. 25th, has eggs again. February 1, young 

 born. Mother has eggs again. 9th, young born. 27th, has eggs 

 again. March 8th, young born. In both these experiments the 

 young were always removed from the vessel in which the mother 

 was kept, as soon as born. On the 2d of November I placed seve- 

 ral ephippia in a glass of clear water. On the 1 0th, two young Daph- 

 niae were born. Isolated one of them. December 12, this Daphnia 

 has given birth to several young, and has eggs again. I8th, has again 

 given birth to several young. 19th, has eggs again. 24th, young 

 born. 25th, has again eggs. January 6, young born. 25th, af- 

 ter two several moultings without producing eggs, has again become 



