less. It is egg-shaped, and has the lip of its mouth prolonged on one side to form a flexible proboscis. The entire surface is banded with longitudinal rows of vilia, these organs being most distinct near the mouth. The general colour is faintly brown, becoming darker backwards. Near the hinder extremity I have noticed a relatively large spherical space, loosely occupied by a globular mass, containing a body of horse-shoe form, which I take to be the nucleus. Under pressure the globular mass was expelled, apparently by a definite passage edged with cilia. Though distorted in the process, the animal quickly resumed its normal shape, and, fallowing the proboscis, turned continuously round its centre. Numerous small vacuoles are usually scattered through the interior. They disappear one by one for half a minute at a time, and then reappear. A constriction running lengthwise along the under-surface gives the body, viewed from behind, a kidney-like outline, the proboscis then curving towards the right. A digestive tract is plainly visible, extending with finely branching channels from the funnel-shaped mouth to what looks like a distinct anal orifice, Mr. Slack's drawing ("Marvels of Pond Life," p. 179} gives an accurate idea of the appearances presented.
Trachelocerea olor, the swan-neck animalcule, is always a pleasing object, as it sails smoothly and deliberately across the field, waving this side and that its long, lithe neck, sometimes backing water for a moment, or curling itself about some fragment of weed in quest of food. In length it may roach 1-40th of an inch; but some specimens are inch smaller. At the tip of the long neck is a short projecting disc, which marks the position of the month, and is armed with a tuft of fine cilia. Near the hinder extremity, which is more or less tapering, I have noticed a contractile space. Occasionally the neck appears forked, due, it has been supposed, to the commencement of fission. On the other hand, it is said that free-swimming Infusoria never multiply by longitudinal, only by transverse fission. The body has its surface prettily chequered, a feature which is still more distinct in an allied genus called Lacrymaria. My specimens of the latter was got in May, in a clay-pit, amongst Sphagnum.
Colpeda cucullus, common in stagnant water, has somewhat the shape of a bean narrowed in front. The cilia are strongest on the fore part, especially at the mouth, which is situated in a depression towards one side. Near the hinder end, which shows no signs of cilia, may be seen a contractile space. Entire minute diatoms are often found mingled with brown or reddish matter in the food vacuoles. The animal is of a rather soft consistence, and puts itself through contortions, during which the greenish granules lining the transparent envelope seem in constant flux. Should a portion of the body carrying cilia become accidentally detached, the fragment continues highly active like an independent being.
Paramecium, from a Greek word meaning oblong, comprises several species which approach more or less to an elliptical figure. Stein has made a special study of P. bursaria. His drawings show equal and similar cilia covering the entire surface, a distinct cortical layer beneath
