bristles. The first segment of the abdomen is small, and carries a fifth pair of feet, modified in both sexes to subserve the reproductive process. In the male the next two segments are distinct; in the female not. The larger antennæ of the male swell out about the middle, and make a hinge-joint behind the swelling, peculiarities wanting in those of the female. The adult female, in the breeding season, carries two external ovisacs, fastened one on each side, near the base of the abdomen. They must not be confounded with the true ovaries, which are internal. They are only a temporary shield, secreted by the female around each bundle of eggs at the time of laving them, and are ruptured and finally shaken off when the eggs are hatched, Lastly, one eye placed in the front of the head serves as the single organ of vision. It is often of a brilliant ruby colour, especially in young specimens.
As in most other genera so in this, the females are much mere numerous than the males. The fact is no doubt connected with another peculiarity, which has been termed parthenogenesis. One impregnation enables a female Cyclops to go on laying successive batches of eggs for life. And the female progeny are themselves fertile, though carefully isolated as soon as born; and so on for several generations. The rate of increase of some species of Entomostraca is enormous, According to Jurine it is quite possible for a single female to he the progenitor during one year of many millions of young, But, practically, the rate of increase is checked by various aquatic enemies, the vast majority of the young being simply born to be eaten. There are few more interesting spectacles under the microscope than the batching of a brood of Cyclops. When the time draws near the little things are seen all huddled together in a cluster, each in its separate pocket of the ovisac, peeping through the membranous veil with bright ruby-coloured eye. You single out one for special observation, and feel a growing interest as you watch the repeated struggles of the tiny prisoner, its final escape, and its first joys of liberty, as it darts away In the surrounding water, with the jerky, zigzag motion of its parent, Nor is if less interesting afterwards to note from day to day the changes of form and successive moultings by which the adult state is reached, Three moultings take place before the animal is perfect, and capable of producing its species.
Nearly related to Cyclops, and not much unlike it in appearance, is Canthecamptus, found abundantly in the ponds about Nottingham. As it is rather small, the best way lo secure a specimen for examination is to place a portion of the gathering in a shallow dish, and look it well over with «a pocket lens. A small dipping tube, made as follows, will be found useful:—One end must be drawn to a blunt point with moderate aperture, the other inserted into a short piece of india-rubber tubing, sealed air tight at the free extremity. The length of the glass part may be about two inches, press the india-rubber between thumb and fore-finger, dip into the water, and by removing pressure at the right moment the object is sucked up into the tube, whence it may be expelled by once more pinching the india-rubber. The two commonest species of Canthecamptus are C. minvtus and C. fareatus. In the female I have often found a curious reddish structure coming off from the sixth body segment. It is of a hard and horny nature, but its use is not known. Closely allied to the preceding is Diaptomus castor, easily recognised by its inferior antennæ, which are "fully as long as the entire body. I have found it amongst algæ in stagnant drains.
Animals belonging to the first two orders of Entomostraca have comparatively few branchia, and these attached to the appendages of the mouth. Animals belonging in the remaining two orders have many branchia, and these attached to the legs, which are often numerous.
