XII.–On some Points in the Structure of Tubifex

Extract

At least two species of Tubifex are abundant in Scotland, one of which is, perhaps, more prevalent in streams, the other in lakes. The former is common at the margin of the river Tay, when the water is low, in sandy tubes of little tenacity, and often in tunnels formed amongst the wet sand under stones, just as many of the marine annelids occur. Its length varies from three-fourths of an inch to an inch and a-half when stretched, and the segments range from fifty to seventy, the average number probably being sixty. The body is of various shades of dull fawn or pale madder-brown, somewhat interrupted by the pale bands at the junctions of the segments, and streaked by the reddish dorsal vessel; or, in summer, marked anteriorly by the whitish mass of the reproductive organs. It is easily recognised amongst its fellows by its faintly purplish or lilac hue, as well as by its peculiar mode of progression; and not a few are observed with reproducing heads and tails. This form, perhaps, has most claim to be called Tubifex rivulorum.