DAPHNIADJB. 
85 
is a disease these little creatures are subject to, the effect 
of which is to arrest their future fecundity. Straus, 
however, has been more fortunate in his observations 
upon this anomalous production, and has proved it to 
be a substance containing two eggs, destined, he says, for 
the future generations of the species in the spring, these 
eggs resisting the cold of the winter, which proves fatal to 
the perfect animal. He says they are generally to be met 
with in the months of July and August. Jurine men- 
tions them as occurring as early as May, and I have found 
them in abundance upon the animals as late as the month 
of November. The description of its formation, given 
by Jurine, is very accurate, though he is wrong as to its 
physiology. 
After the third moulting has taken place, we may see a 
green matter in the ovaries, which differs both in colour 
and appearance from that of the eggs. After the fourth 
moulting this green matter passes from the ovaries into 
the matrix or open space on the back, and there spreading, 
forms the ephippium. At first it is of a grayish colour, 
and some hours after becomes of a black hue. When 
examined by the microscope, it appears of a dense texture, 
composed of a sort of network of hexagonal cells. In the 
centre of this opaque mass we see one or two round or 
rather oval bodies, called ampullae by Straus, who says 
they are capsules, opening like a bivalve shell. In each 
of these bodies is contained an ovum, covered with a horny 
shell, by which means they are protected from the severity 
of winter, and enabled to resist an intensity of cold which 
kills the parent. 
At the fifth moulting the animal abandons the ephip- 
pium, which floats on the surface of the water, and re- 
mains, with the two eggs inclosed, till next spring, when 
the young are hatched by the returning warmth of the 
season. “ These two kinds of eggs/' says Straus, “ pro- 
duced by the same animal, offer a very singular example 
in the history of animals, and show with what wisdom 
nature provides for the preservation of her smallest crea- 
