STUDIES ON EARTHWORMS. 243 
III. Toe Variations IN THE Srructure or EartHworMs 
TREATED ACCORDING TO THE Dirrerent SysteMs OF 
ORGANS. 
The Sete.—Claparéde (12) drew his characters for the 
Terricolz as opposed to the Limicolz, from Lum bricus, some 
of which characters are now known to hold only for that genus, 
others for only a few genera, and amongst them is the arrange- 
ment of the sete in four groups of two setz in each somite. 
This arrangement holds for many Earthworms, viz. Lum bri- 
cus, Anteus, Rhinodrilus, Eudrilus, Acanthodrilus, 
Digaster, and Moniligaster, including, therefore, forms 
from each of Perrier’s groups (14). 
In Urocheta, Titanus, and Acanthodrilus capensis, 
and in the doubtful Alyattes, and Eurydame of Kinberg, 
the same arrangement holds in the anterior part of the body, 
but varies posteriorly ; the setee become scattered in Titanus, 
Ac. capensis, Alyattes, and Eurydame, but remain in line, 
whilst in Urochzta they become scattered but alternate in 
consecutive somites. 
In Aigesipyle, again one of Kinberg’s doubtful genera, 
they are scattered (that is, the two sete forming a couple 
become separated), except the anterior ventral couples. 
In Acanthodrilus kerguelenensis the sete are sepa- 
rate except in the genital somites. 
In Pontodrilus throughout the body the ventral couple 
(setze 1 and 2, counting from the mid ventral line) remain close 
together, but setee 3 and 4 are separated. 
Again, in Plutellus the eight setz are nearly equidistant, 
but do not alternate, whereas in Pontoscolex there are only 
seven sete in each somite, which alternate in consecutive 
somites throughout the body, and in Geogenia they alternate 
anteriorly only. In a form which I shall describe in a later 
paper, seven out of the eight alternate, whilst the ventralmost 
setee (No. 1) remain in line throughout the body. 
