90 
ON A NEW SPECIES OF NAIDIFORM WORM, 
TJero roseola. 
By G. F. Nicholls, D.Sc., F.L.S., 
lTofessor of Biology in the University of Western Australia. 
When engaged, recently, in examining a number of samples of 
muddy water in search of protozoa for class purposes, [ came upon 
several specimens of a very slender and elegant naidiform worm. 
In view of Michaelsen’s statement (1907, p. 118) that in the 
south-western portion of Australia, the fluviatile Oligochseta are 
very rare, my attention was at once arrested by the discovery. The 
particular sample of water was one taken from a horse-trough in 
South Perth. This trough proved, upon inquiry, to be fed by an 
inlet pipe connected with a deep bore (1,800 feet), the water from 
which is highly mineralised* and has, at the surface, a temperature 
of 1 03° F. 
Further samples of the sediment from the bottom of the trough 
were taken and showed the worms present in great numbers, several 
hundred being obtained in a single dip of a large test tube. Assoc- 
iated with them were an unidentified ( 'hoe to gas lev, and many 67m*- 
onomus larva?, while the surface of the sediment was crowded with 
a large Ostraeod and abundant Cyclops, the latter heavily infested 
with an Epistylis. 
On allowing the mud to settle, the worms were found, to collect 
in dense aggregations against the side of the vessel (Fig. 1), form- 
ing conspicuous pink masses. The anterior end of most was thrust 
downwards into the sediment, while the greater part of their length 
swung up more or less vertically with cont inuous swaying movement. 
Nearly transparent, the worm (Fig. 2) appears by transmitted 
light of a delicate pink colour, due to the contained blood, and at 
once recalled the beautiful Dero f ureal a which 1, at first, supposed 
it to be. It has at its posterior end a pair of ventral ly situated, 
elongate cylindrical palpi, which are extremely mobile. Lateral and 
dorsal to these are three pairs of well developed branclme, richly 
ciliated (Figs. 4, 5). Together these structures form a fringe to 
the funnel-shaped chamber into which the intestine widens at its 
posterior end. All are contractile, the branchiae especially so, and in 
preserved specimens they usually appear only as short thick knobs 
int limed and almost withdrawn into the anal chamber (Fig. 4). Two 
of these branchial processes on either side are of practically equal 
length, but the most anteriorly situated pair, springing from the 
d.orso-lateral surface of the anal funnel, are somewhat shorter. In 
* Analysis of the water reveals 96 parts solid per 10,000. 
