FAM. 2. _Enchytraeidae._[431]—This family consists at present of rather over fifty well-characterised species, which are distributed into eleven genera. It is common in this country and in Europe generally; it has been met with in Spitzbergen and the extreme north; it occurs in the American continent from the north to the extreme south; it is also an inhabitant of New Zealand. The worms of this family are nearly always of small size, sometimes minute; they never exceed an inch or so in length, and that is a rare occurrence. They are equally at home in water and in soil, some species being common to the two media; a few are marine or littoral in habit, while others are parasitic in vegetable tissues. Like most earthworms, and unlike the majority of aquatic worms, the chaetae are without a bifid termination; the body-wall, too, is comparatively thick. The perivisceral fluid is often (as in certain Naids) loaded with elliptical or rounded corpuscles. Resemblances to earthworms rather than to the aquatic families of Oligochaeta are suggested by the long distance which separates the {376}spermathecae from the male pores (segments 5 and 12), and by the paired or unpaired glands that have been already compared to the calciferous glands so universally present among earthworms. On the other hand, the male ducts are confined, as in the lower Oligochaeta, to two segments, upon one of which the internal, upon the other the external orifice is situated, and the oviduct is reduced to a simple pore, as in Naids; but this may be merely a matter of convergence by degeneration. Perhaps the most remarkable genus in the family is _Anachaeta_, which has no chaetae, but in their place a large cell projecting into the body-cavity, which appears to represent the formative cell of the chaeta. The integument of this genus contains true chlorophyll, according to Vejdovsky. A singular character, found, however, also in _Rhynchelmis_ and _Sutroa_ among the Lumbriculidae, is the opening of the spermathecae into the alimentary canal. This was originally discovered by Dr. Michaelsen, but has been abundantly confirmed. _Stercutus_ is a singular genus which was originally found in manure, and has the peculiarity that the alimentary canal is often aborted; this degeneration seems to bear some relation to the food and conditions of life.