186
BRITISH ANNELIDS.
Out of the hundreds of dendrobaenic forms examined from all parts
of the kingdom, during every period of the year, I have hitherto
failed to observe these organs. The forms which frequent trees
secrete a small quantity of yellow fluid from the dorsal pores, but
several of the terrestrial forms of the same species are incapable of
doing so. This is another curious fact which merits further investi-
gation.
There are four well-marked species known to occur in Great
Britain, in addition to five forms or varieties. I shall be obliged
to depart from the arrangement adopted in my memoir referred to
above in some points, owing to the discoveries which I have made
since its publication. I formerly proposed the "Celtic Worm"
(Allolobophora celtica, Rosa) as the type of this group ; but I now
prefer, for reasons to be given hereafter, to go back to Eisen's type
(Dendrobaena boeckii), and base our English species thereon. Un-
fortunately, this species is at present unknown to Essex. In the
following enumeration, I shall specify all the British forms known
to me at the close of 1892, giving localities for those only which are
found at present in Essex.
1. Boeck's Worm (Dendrobaena boeckii, Eisen). The
original description of this worm as a new species and genus ap-
peared in 1873. The genus was separated from Allolobophora chiefly
on the ground that the setae were wide apart. This character, how-
ever, is variable, and we find in other species of worms, as, for
example, A. profuga, Rosa, a similar arrangement. Eisen gives this
brief account of the genus. "Male pores on segment 14 (=15
English method), setae everywhere equidistant, except in the case
of the two highest (on the back), which are somewhat wider
apart than the others. The lip cuts into the peristomium to a
distance of three-fourths the diameter." He says the species under
description is the same as Lumbricus puter, Eisen, an account
of which he had published two years before. The girdle in the
type occupies, as a rule, the five segments 29 to 33, three of
which (31, 32, 33) carry the clitellar papillae (tubercula pubertatis).
The anal segment is somewhat pear-shaped. The lip cuts deeply into
the first ring, but does not completely bisect it. There are some-
what prominent papillae carrying the male pores. The first dorsal
pore is well seen between the fifth and sixth segments. The worm
is about one and-a-half inches, or twenty-five to thirty-five milli-
metres, in length, and contains a total of eighty to 100 segments.