NOTES ON SOME AQUATIC OLIGOCHATA. 209 
till I obtain other specimens from Barking before giving a new 
name on these grounds. 
I find no chetz, either dorsally or ventrally, in Segment x1 
in mature worms. 
In Segment x the ordinary ventral chet are replaced in 
mature forms by a single long rod-shaped cheta on each side, 
immediately in front of the pore of the spermatheca.' 
I do not find the “ dilatations ”” which Vejdovsky figures on 
the sperm-duct between atrium and penis so long as the 
duct is uninjured ; when, however, it is separated from the 
body of the worm by pressure there is a variable number of 
dilatations, as in Heterocheta. 
Note on Chetez of Tubifex rivulorum. 
Professor Lankester” was the first to record the existence of 
secondary prongs or teeth in the fork of the dorsal chetz of 
this worm, and mentions a web passing between the two main 
prongs. I have not been able to detect this web, but have not 
had a very large series of specimens under observation for this 
purpose. I treated the chetz in the usual way, i.e. I dis- 
solved the worm, on a slide, in KHO, mounted the chetz in 
glycerine, and examined them with a Zeiss’s homogeneous 
immersion lens, but I was quite unsuccessful. It is not 
impossible that the specimens which Lankester examined 
belonged to Hisen’s genus Ilyodrilus, in which such a mem- 
brane exists. But I have noted some peculiar modifications of 
these dorsal chetz, which I figure in Pl. VII, fig. 34, a, 4, 
c,d; one of the most curious of which is the occurrence in 
more than one case of a tooth outside the chief prong. 
Stylodrilus Vejdovskyi, n. sp. 
In a gathering made on July 17, just below Goring-on- 
Thames, I found a few small red worms about one third the 
1 Since writing this paper I have seen Dr. Antonin Stole’s memoir on 
Bohemian Tubificide, in which he figures this cheta, which is grooved 
distally, and is inserted in a sac into which a pair of glands open, close to the 
pore of the spermatheca. 
2 Loe. cit. 
VOL. XXXIII, PART I.— NEW SER. 
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