How these animals can live for months in the muddy, impure water is to me a puzzle. They are very sluggish, possessing none of the quick motions of their allied _C. bartonii,_ for when taken out and placed either in water or on the ground, they move very slowly. The power of throwing off their claws when these are grasped is often exercised. About the middle of May the eggs hatch, and for a time the young cling to the mother, but I am unable to state how long they remain thus. After hatching they must grow rapidly, and soon the burrow will be too small for them to live in, and they must migrate. It would be interesting to know more about the habits of this peculiar species, about which so little has been written. An interesting point to settle would be how and where it gets its food. The burrow contains none, either animal or vegetable. Food must be procured at night, or when the sun is not shining brightly. In the spring and fall the green stalks of meadow grasses would furnish food, but when these become parched and dry they must either dig after and eat the roots, or search in the stream. I feel satisfied that they do not tunnel among the roots, for if they did so these burrows would be frequently met with. Little has as yet been published upon this subject, and that little covers only two spring months--April and May--and it would be interesting if those who have an opportunity to watch the species during other seasons, or who have observed them at any season of the year, would make known their results. RALPH S. TARR * * * * * OUR SERVANTS, THE MICROBES. Who of us has not, in a partially darkened room, seen the rays of the sun, as they entered through apertures or chinks in the shutters, exhibit their track by lighting up the infinitely small corpuscles contained in the air? Such corpuscles always exist, except in the atmosphere of lofty mountains, and they constitute the dust of the air. A microscopic examination of them is a matter of curiosity. Each flock is a true museum (Fig. 1), wherein we find grains of mineral substances associated with organic debris, and germs of living organisms, among which must be mentioned the _microbes_. Since the splendid researches of Mr. Pasteur and his pupils on fermentation and contagious diseases, the question of microbes has become the order of the day.