There are many other genera and species of fresh-water polyzoa besides the _Plumatella repens_, and they are found attached to sticks, stones, or leaves, generally to the under surface of the latter. They are all objects of great interest and beauty, which, whatever their diversity, conform sufficiently to one type that the student who has observed one, will easily recognise the zoological position of another. They should be viewed by transmitted and by dark-ground illumination, which produces very beautiful effects. To observe them in the performance of their functions, they require more room than the live-box can afford, but are well shown in the glass trough, whose moveable diaphragm enables them to be brought near enough to the object-glass, for the use of a power of about sixty linear for general purposes, and of from one to two hundred for the examination of particular parts. For a more detailed examination dissection must be employed, but all that we have mentioned can be seen without injury to the living animal, if specimens are kept till new cells are formed in water, which does not contain enough dirt to render their integuments opaque. CHAPTER XII. DECEMBER. Microscopic Hunting in Winter--Water-bears, or Tardigrada--Their comical behaviour--Mode of viewing them--Singular gizzard--A compressorium--Achromatic condenser--Mouth of the Water-bear--Water-bears' exposure to heat--Soluble albumen--Physiological and chemical reasons why they are not killed by heating and drying--The Trachelius ovum--Mode of swimming--Method of viewing--By dark-ground illumination--Curious digestive tube with branches--Multiplication by division--Change of form immediately following this process--Subsequent appearances. There is always satisfaction in finding a work accomplished; but the attempt to delineate some of the marvels of minute creation has been a pleasant one, and we approach the completion of our task of recording a _Microscopic Year_ with something like regret. The dark, dirty December of the great metropolis may not seem a promising time for field excursions, but some ponds lie near enough to practicable roads and paths to render an occasional dip in them, not of ourselves, but of our bottles--an easy and not unpleasant performance; and if the weather is unusually bad, we can fall back upon our preserves in bottles and tanks, which seldom fail to afford something new, as we have been pretty sure to bring home some undeveloped germs with our stock of pond-water and plants, and even creatures of considerable size are very likely to have escaped detection in our first efforts at examination.