BRITISH ANNELIDS.
33
tion. It lives among the roots of grass on the margins of stagnant
or running water, and is often with difficulty distinguished from the
mud-covered rootlets. To what extent its colour is strictly protective,
or due to its food and other factors, is not yet ascertained; but it is
known to vary greatly. I have found a rich golden variety in Cum-
berland and Yorkshire, while elsewhere I have obtained specimens
ranging from a dull brown to a bluish, iridescent colour through a
dull yellow and red. Large series from every possible locality, with
exact data respecting habitat, must be studied before we can venture
on an opinion in the matter of cause and purpose. The varieties are
widely distributed, for, in addition to my own records, I have notes of
their appearance in Hungary, Scandinavia, and elsewhere.
The girdle of Allurus, which commences on segment 22 and ends
on the 27th, is rather nearer the head than the tail. The latter portion
of the body is angular, and usually consists of about forty segments,
so that an entire, full grown worm should contain about seventy or
eighty rings. I have found as many as ninety segments on a large
specimen. The male pore may be easily detected on either side of
segment 13, running parallel with the rings. The lip does not per-
fectly bisect the first ring. As I do not intend to refer to internal
anatomy in these papers as a means of identification, I shall be con-
tent to direct the reader's attention to the details and references
supplied in my article, already quoted, where its distribution so far as
known last year is also detailed.
I may properly close this paper with a brief systematic description
of the external characters of the "Square-tail" worm.
Name, Allurus tetraedrus (Eisen, 1870). Length one to two
inches. Colour usually a dirty brown, but variable. Normal num-
ber of segments 70 to 80, the girdle occupying 20 to 27. Male
pores on papillae, laterally on segment 13. Lip (prostomium) rounded
in front, delicate, ramified with blood vessels, only partially cutting
the first segment (peristomium). Hinder extremity angular with a
pair of setae at each angle, about 40 segments behind the girdle.
Setae of three kinds, viz.: the ordinary bristles, penial setae on
segment 8, and small claws or spinets. First record for Essex,
December 5th, 1888, Rev. O. P. Cambridge, B.A., confirmed by Dr.
Benham and H. Friend.