BRITISH ANNELIDS. 237
embryonic, those useful to the organism in its early stages ; (ii.) the
vestigial, those useful to its ancestors, but now in process of abortion
through the operation of the law of economy of nutrition ; and (iii.)
the indifferent ancestral structures, structures originating in the vari-
ation which we call 'spontaneous' of its ancestors; which, being
neither directly useful nor extravagantly wasteful of tissue—and there-
fore likely to become aborted—nor otherwise harmful, are inherited
unaltered. The indifferent class similarly includes all structures
originating in the free play of that 'spontaneous variation' which
Mr. Wallace has shown to be so widely varied in its results, which
are neither directly useful nor harmful. Darwin showed that struc-
tures which I should refer to one or other of these classes, being
practically beyond the scope of natural selection, will be extremely
variable. Coming to Mr. French's immediate subject, I would
remark that he has confined his attention to the two species of
Dipsacus that happen to be British, whereas there are seventeen or
eighteen species of the genus, five or six of which occur on the con-
tinent of Europe; and that D. sylvestris and D. pilosus belong to
different sections of the genus, the Eudipsaci and the Trichocephala,
the latter approximating to the genus Cephalaria, I should be
interested to know whether Mr. French has ever observed the two
British species, or others, growing so as to compete with one another."
—G. S. Boulger.]
BRITISH ANNELIDS.
WITH ESPECIAL REFERENCE TO THE EARTHWORMS OF ESSEX.
By REV. HILDERIC FRIEND, F.L.S.
(Continued from page 196.)
ONLY a few words are necessary in order to present a bird's eye
view of the different genera of British earthworms. The indi-
genous species belong entirely to one group, which has been, at the
most, divided into four sections, and as one of these divisions is not
at present retained (though it may at any time be revived), we have
practically only three distinct genera to examine. These are Lum-
bricus, Allolobophora, and Allurus. The lapsed name is Dendro-
baena, but we will not include it in our present study. Lumbricus
is distinguished from Allolobophora chiefly by the shape of the lip or
prostomium. In Lumbricus the foremost portion of the body and
the first ring form a perfect mortise and tenon, whereas in Allolobo-
phora the lip cuts but partially into the first ring. The first ring,
which bears no sets, is usually known as the peristomium. While
1 This I have not yet seen.—J. French.