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VI. An account of the Two Methods of Meproduction in Daphnia, and of the Structure 
of the Ephi])pntm. By John Lubbock, Esq., F.G.S. Communicated hy Chaeles 
Daewin, F.R.S. 
Eeceived December 22, 1856. — Eead January 29, 1857. 
The genus Daphnia is a small group of freshwater Entomostracous Crustacea, which has 
long been celebrated for possessing the power of reproduction without the intervention 
of the male, and for laying two different sorts of eggs. In both cases the eggs pass from 
the ovary into a space or receptacle between the carapace and the back of the animal. 
The carapace, according to Milne-Edwaeds, is an excessive development of an anterior, 
probably the mandibular segment * which encloses the whole of the posterior part of the 
body, which lies freely in it, as it were m a bivalve shell. This bivalve shell or carapace 
is widely open below and behind, but is closed along the back, and as it forms there a 
regular arch, and does not follow the sinuous margin of the back of the animal, there is 
left between the back and the carapace an open space or receptacle, into which the eggs 
are laid, and in which they remain until the young Daphnia is sufficiently developed to 
be able to swim about by itself. 
This “ receptacle ” is freely open to the surrounding water, but the eggs are prevented 
from falling out by a tongue-like projection, developed evidently for that purpose from the 
back of the animal. VTien, however, the young are ready for exclusion, the mother has 
but to depress her abdomen, and they easily shp from the receptacle into the open water. 
Although both the common or agamic f and the ephippial eggs are thus protected by 
the carapace or valves until they are hatched, there is this difference, that the agamic 
eggs are carried about by the animal, and shortly before the next shedding of the skin, 
the young which have in the meantime been hatched swim away ; while for the ephip- 
pial eggs, part of the carapace is speciahzed into a pod-like or saddle-shaped box called 
the ephippium, in which, when the skin is changed, they remain for some time before 
being hatched. 
Several of the earher naturahsts, and more recently Dr. Baied, in his excellent 
‘ History of British Entomostraca,’ have detailed observations clearly showing that the 
ordinary eggs are produced, and are fertile, without the intervention of the male, but 
the mode of production of the ephippial eggs has never been correctly described ; nor 
* See Ann. des Sc. Nat. 1851, p. 234. 
t The agamic eggs certainly do not require impregnation, and I shall give my reasons presently for 
believing that the male influence is necessary to the hatching of the ephippial eggs ; but this is not proved, 
and it is therefore just possible that both sorts of eggs may be agamic. 
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