DAPHNIADiE. 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. Tlie description of its formation, given 

 by Jurine, is very accm-ate, 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 tlie 

 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- 



