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cast along with it; and, floating on the water, preserves the eggs through the cold season, till they are hatched by the returning warmth of spring.
In July, 1870, I found in a shallow pool on the turfy soil of Lindow Common}, Cheshire, a good many examples of one of the Daphnia family, which, from its long bristles, bears the name of Macrothrix. My specimens corresponded to Baird's description, except that a particular bristle mentioned by him was wanting in my captive. I had possibly chanced upon a new variety. The superior antennæ are of considerable size, hanging from the beak like two flat swords, with a broad, straight-edged extremity. While watching an example in the live-box, what was my astonishment to observe some of the parts suddenly became double, One after the other, the hinder segment, its hooked spines, the beak, superior antennæ, and so on, appeared double; and it became evident that I was the fortunate witness of the moulting process. I at once mounted the whole affair in glycerine, and my Macrothrix now lies side by side with its cast-off skin.
One other family of the Cladocera should be mentioned, if only because it contains Chydores sphæricus, a very common species in our stagnant ponds. The Lynceidæ (for so the family is called) may he recognised by a black spot situated in front of the eye, and looking not much unlike a second eye, which, however, it is not. The intestine, moreover, makes one complete turn and a half. To the same family belong Eurycercus lamellatus and Acroperus herpæ, both of which occur in this neighbourhood. The latter is fond of resting on the top of the water, moored by its antennæ to a bit of weed; or a cluster of them will collect round some floating leaf or sprig, and he motionless in the warm sunshine as if asleep.
Of the last order, Phyllopoda, we shall cite only one example, Cheirocephalus diaphanus, or the Fairy Shrimp. I have not yet seen it alive, but those who have speak with enthusiasm of its singular beauty. The male is especially gorgeous. With regard to anatomy, the body is destitute of a carapace, and is divided into many segments, affording great freedom of movement. The male has a remarkable pair of inferior antennæ, employed essentially as clasping organs. Those of the female are simpler, being shaped like a broad sickle, There are two stalked eyes, each composed of an immense number of lenses, showing a further advance towards the insect type. Its young, however, has but one simple eye, placed centrally in front of the head. This is represented in the adult by a dark blind spot. No fewer than eleven segments compose the thorax, to each of which is attached a pair of branchial feet, of a broad and leaf-like form. The tail consists of two broad appendages; and both feet and tail are thickly beset with plumose hairs. Extending from the head to near the tail may be discerned about eighteen or nineteen small hearts, or quasi-hearts, placed end to end and all moving together. The female possesses a single external ovary, from which, at the proper time, from 100 to 400 eggs are jerked out in succession during twenty-four hours. When hatched the young undergo a series of moultings and changes of form before they finally resemble their parent.
We have now completed our illustrations of freshwater Entomostraca. I shall not at present enter into any description of the marine kinds. Specimens of their empty carapaces, particularly of the Ostracoda, may be found in the sand of our coasts, and will often occur to the searcher after foraminifera. I have thus obtained examples of Cythereis and Cythere. I have also taken, near Penmaenmawr, a good many Cetochilus, a rather striking form resembling Cyclops.
The Entomostraca have played an important part in the life-history of the globe from the earliest epoch to the most recent. They have been