Studies on Earthworms. - Journal of Cell Science

216 WILLIAM BLAXLAND BENHAM.
a. The presence of nephridia in the same somites with the
genital ducts (except in some species of Perichseta and
Pleurochseta (Megascolex), where nephridia are unknown
in any somite, and in Pontodrilus, in which the nephridia
are said not to commence 1 till the hinder region of the sperm
duct, so that there are none in the somite carrying the oviduct).
b. The abundant vascular network on the nepridia and body
wall.
c. The almost universal presence of a gizzard (Pontodrilus
is again an exception).
d. The much smaller size of the ova and the compactness of
the ovary.
But even these charcters may have to be altered as new
forms are studied.
These Lumbricinas Perrier divides into four groups,
taking as a basis the relation of the clitellum to the male pore.
1. The Anteclitelliani (Preclitelliani), in which the male
pore is far in front of the clitellum, include the genus Lumbricus,
which Eisen (15) has lately subdivided into the genera
Lumbricus, Allurus, Allolobophora, andDendroboena,
as well as, doubtfully, Kinberg's (19) genera Alyattes and
Eurydame, and Savigny's (1) Hypogseon. As these three
latter genera are insufficiently described, it is doubtful whether
the characteristics given by these authors justify the retention
of their names.
Whilst this group contains only a few forms, the members
of the other groups are numerous and mostly of extra-European
origin.
3. The Intraclitelliani, where the male pore is situated
within the limits of the clitellum, include the genera Anteus,
TJrochseta, Rhinodrilus, Microchseta, and perhaps
Kinberg's Greogenia and Tritogenia.
3. The Postclitelliani have the male pore behind the
clitellum, and include Perichseta, Acanthodrilus, Eudri-
1 It is not improbable that examination by means of microscopic sections
would result in the discovery of nephridia in some cases where Perrier has
failed to see them with the naked eye.