244 WILLIAM BLAXLAND BENHAM. 
In Echinodrilus we have still four groups, but there are 
five setze to each group. 
In Hy pogeon, Savigny described nine equidistant sete, of 
which oue was said to be in the mid dorsal line. 
In Tritogenia, Kinberg, only six sete are present in each 
somite. The number is greatly increased in Pericheta, 
where there may be as many as 100 to the somite, and in 
Perionyx therearethirty. These in each case are equidistant 
and form a complete ring round each somite. 
In Megascolex, again, this arrangement is varied by an 
interruption in the ring in the mid dorsal line, whilst in Bed- 
dard’s Pleurocheta, as well as this dorsal break, there is a 
similar break ventrally. 
The setz are not always simply pointed, as Claparéde sup- 
posed, but in many cases are variously ornamented, as in Rhi- 
nodrilus, throughout the body ; in the genital sete of Uro- 
cheta and of Alcanthodrilus; whilst in Urocheta all the 
sete are bifid at their free extremity. Moreover they are 
modified in certain parts of the body, as Hering (5) has shown, 
for copulation: e. g.in Lumbricus, on clitellum, and on the 
somites xv and XxvI. 
Pores.— Perrier has pointed out a sort of relationship between 
the nephridiopores and the couples of setz ; in some genera 
these pores are in front of and slightly dorsad of the ventral 
couples (sete 1 and 2), as in Lumbricus, Titanus, Ponto- 
drilus, whilst in other genera the pores have a similar relation 
to the lateral couples (8 and 4), Rhinodrilus, Eudrilus, 
Acanthodrilus, Anteus, Moniligaster [also in Micro- 
cheta]. 
Plutellus is exceptional at present in showing an alterna- 
tion of the nephridiopores with the seta 2 and with seta 4 in 
consecutive somites, whilst the first few pairs are in line with 
the third seta. Again, they are, in Urocheta, related to the 
third seta throughout the body. They remain in this line even 
when the setz alternate, though one would expect, if there 
were any relation between them and the setz, that the nephri- 
diopores would also alternate. 
