NOTES ON SOME AQUATIO OLIGOCHATA. 207 
Spirosperma ferox, Eisen.! 
This worm has hitherto been found only in Sweden, and 
has been observed by Eisen alone.? 
I have found specimens in the Thames and in the Cherwell. 
It is readily recognised by the naked eye, owing to its grey 
colour, with a bright white clitellum occupying Segment x1, 
and extending into x and x11. The grey is sometimes less 
marked, apparently in immature specimens, which are greyish 
red. The grey colour is due to numerous closely set papilla, 
of rather irregular form, usually irregularly rectangular, with 
long axis, as Eisen states, at right angles to the worm’s length ; 
but they are not “dark,” as he says. They look dark by 
transmitted light, but if the surface is viewed by direct 
reflected light they are white, the dark colour being due to 
the feebly yellow globules in the papille. 
The worm is six eighths of an inch long, and relatively thick 
anteriorly. The chief anatomical point is that the chete of 
the dorsal bundles throughout the body are capilliform, 
accompanied by, in most cases, extremely delicate webbed 
cheetee. These are rather stouter in the first half-dozen seg- 
ments than posteriorly, but throughout they are less than 
half the thickness of the capilliforms (fig. 36, c, d). 
The shape of these “ webbed ” chetz is quite distinct from 
the multidentate, or even the webbed chete of Tubifex, or 
the palmate chete of Psammoryctes and Heterocheta, 
though they approach the latter. 
The ventral chete are not all alike (fig. 36, e,f); they 
are all crotchets, but in the first six bundles the proximal 
prong is shorter than the distal prong (f). Behind the reverse 
is the case, and the proximal prong is extremely stout and 
strongly recurved (e), somewhat as in Psammoryctes, but 
more so. 
The capilliform cheetz are usually four per bundle up to 
1 “Oligochzetological Researches,” ‘Annual Report of the Commissioner 
of Fish and Fisheries for 1883,’ Washington, 1885, 
? Stole has found it in Bohemia, 
