A NEW BRANCHIATE OLIGOCHATE. 327 
one pair to each segment. In the largest of the three worms 
there were at least eighty of these processes oneach side. Here, 
again, I am unable to be absolutely accurate; the processes 
first appear as mere mammillary outgrowths, which gradually 
increase in length upon successive segments; it is difficult, 
therefore, to say exactly when they begin. From being the 
slightest elevations, barely perceptible, of the integument, the 
processes become nearly as long or even longer than the dia- 
meter of the worm’s body: they then gradually diminish in 
length towards the anus; but they are not so small at the 
finish as at the beginning, nor are there so many rudimentary 
branchiz at the anal end of the series as there are at the oral 
end. In one specimen, with only twenty pairs of branchie, there 
were no rudimentary ones at the posterior end of the series. 
By a remarkably fortunate accident, the water which pro- 
duced the specimens of Branchiura Sowerbyi contained 
also three or four examples of Bourne’s Chetobranchus. I 
have, therefore, been able to compare the two forms, detail for 
detail, though I have convinced myself that Bourne’s excellent 
description really rendered an examination of the worm Che- 
tobranchus itself unnecessary. 
The first important difference, then, between the branchial 
processes is a difference in position. In Chetobranchus 
the branchie are anterior, gradually diminishing and 
finally disappearing posteriorly; in Branchiura 
they are developed upon the last sixty segments of 
the body or so. 
In examining the living Chetobranchus it is easy to see 
that, as Bourne has described and figured, the sete are con- 
tained within the branchiz. The long capilliform seta of the 
dorsal bundles reaches nearly to the end of the branchia. In 
Branchiura there is no connection at all between the bran- 
chial processes and the sete. The branchie are, in fact, not 
latero-dorsal in position, as in Chetobranchus; they arise 
from the body-wall dorsally and ventrally in the middle line. 
In the figure which illustrates the living worm (fig. 2) the 
anus is shown to one side of the body apparently ; the worms 
