DAPHNIADiE. 
83 
it takes place in the young every two days, which agrees 
very nearly with J urine’s experiments, performed in the 
month of June. In winter the intervals are somewhat 
greater. In the month of December I found, when kept 
in a vessel in my room, the intervals thus : December 8th, 
young one born ; 12th, moulted for the first time; 14th, 
moulted a second time; 17th, moulted a third time; 
21st, moulted a fourth time, and has eggs ; 29th, moulted 
a fifth time; January 9th, moulted a sixth time; 19th, 
moulted for the seventh time. In a young D. pulex, born 
from an ephippial egg, the intervals were as follow : 
December 5th, young one born ; 13th, moulted for the 
first time; 17th, moulted a second time ; 24th, moulted 
a third time ; January 3d, moulted a fourth time, and has 
eggs ; 11th, moulted a fifth time ; 18th, moulted a sixth 
time. 
Each time it moults it increases in size, the moulting 
being evidently necessary for the gradual growth of the 
animal. The process does not seem to stop, however, 
when it has acquired its full growth, but, as far as I am 
able to judge, continues during its whole life, even long 
after it has gained its full size. The shell of the adult 
Daphnim, when in very stagnant waters, soon becomes 
overgrown with moss or parasitic infusoria, and thus 
the animal’s motions become much impeded, and at 
last entirely destroyed ; the moulting, therefore, seems to 
be necessary in the full-grown animal for the preservation 
of its life, for weak or sickly individuals may be seen 
frequently so overgrown with Confervse, &c., that motion 
and life are both soon arrested, the little creature appa- 
rently not having strength enough to throw off its exuviae. 
At the fourth moulting* the young insect has eggs, which 
are deposited in the open space on the back, almost im- 
mediately after the old shell has been cast off. The time 
that the eggs remain there varies according to the season 
of the year. In summer, according to Jurine, three days ; 
* Straus says after the third; Jurine, generally between the third and 
fourth. I have invariably found it to be immediately after the fourth. 
