NOTES ON SOME AQUATIC OLIGOCHATA. 189 
and Vejdovsky makes no remarks upon it, merely giving 
Claparéde’s diagnosis almost textually (‘System und Morph. 
d. Oligocheta,” p. 84). Vaillant, in the ‘Hist. nat. d. 
Annélides,’ has no more to say of it. 
In the above diagnosis there is one error, which I will point 
out at once. The chetz referred to as “ becherformig ” are 
not cupped; they are what is known as fan-shaped (or 
palmate, as I shall call them), such as are characteristically 
found in Psammoryctes. 
I have been able to extend our knowledge of this worm, and 
will now give my own observations on Heterocheta. 
During life the worm is pink in colour, the sperm-sacs and 
ova in mature animals showing up white. 
The length is about five eighths of an inch when fully mature, 
and exceptionally slightly longer ; but I have seen none that 
attain a length of one inch. The white region which marks 
the position of the genital cells occupies about one eighth of 
an inch, commencing about the same distance from the 
anterior end (fig. 1). The number of segments is about 
forty. 
In habit it resembles Hemitubifex, &c., amongst which it 
lives; and I found it sometimes by itself in the mud, with 
posterior end protruded therefrom, as is the habit of other 
members of the family, or twisted and coiled amongst the 
Hemitubifex in the “ balls”’ which the latter form. 
When disturbed, an individual will roll itself into a spiral, 
or twist itself into a knot (fig. 2). 
It is not by any means easy to distinguish Heterocheta 
by the naked eye from such forms as Paranais littoralis, 
Pachydrilus, or even some paler forms of Hemitubifex. I 
have found it impossible to identify them without picking them 
out and using a low-power microscope for their examination ; 
and even then, unless they happen to present their dorsal sur- 
face to view, it requires great practice to appreciate the exact 
shade of pink which serves to distinguish them from the other 
worms mentioned above. 
If, however, the back is uppermost, then one can readily 
