BRANCHIURA SOWERBYI BEDDARD. 295 
ina dish they appeared to move and coil themselves up in the same way as perfect 
individuals (see below). 
A possible explanation of this curious circumstance seems to be that by the expulsion 
of the genital products, which apparently takes place towards the end of February, the 
anterior segments of the body are so much damaged that they die and are thrown off ; 
the worms, however, continue to live, though it may be doubted whether they are 
capable of regenerating the anterior end; probably they die after a time, and the 
whole generation thus perishes each year. 
On touching any part of a mass of these worms they cease their waving movements ; 
a feeble disturbance merely causes them to hold themselves rigid, while a more violent 
one causes a general contraction of all the individuals. Contraction also takes place if 
the mud near them be disturbed. It looks, at first sight, remarkably easy to scoop up 
a number of the worms; but as soon as the spoon touches the mud the waving tails 
vanish in a flash, and however quickly the scoop be made, probably few will be ob- 
tained. This, of course, is not the case with the large masses described above, which 
are so tightly intertwined that they cannot escape thus. The same waving movements 
and sudden contractions are seen in the worms kept in a vessel in the laboratory, where 
a slight jarring of the table is sutticient to arrest the movements. Isolated individuals 
usually coil themselves up into a spiral on being disturbed. 
External features.—The usual colour is a pale reddish brown, deeper anteriorly 
than posteriorly ; by reflected light under a low-power binocular microscope the posterior 
part of the body often has a patchy, opaquish yellow colour, which has the appearance of 
being due to a golden-bright granular deposit on the inner surface of the body-wall ; it 
is probably in reality a deposit in the peritoneal cells. Some specimens from the foul 
pools mentioned above were black in their posterior half; and it may be mentioned, by 
way of comparison, that | have found Clitellio arenarius, usually of a red colour, 
completely black when inhabiting a part of the shore contaminated by sewage. 
The length of the worms when extended may be as much as three inches; smaller 
Specimens measure one and a half or two inches. ‘Their greatest breadth is less than a 
millimetre. The number of segments is commonly about 110 ; there isa double annula- 
tion in the first few. ‘The prostomiwm is bluntly conical. The cleted/wm includes the 
eleventh with more or less of the twelfth segment. 
The setzx (fig. 9) of both dorsal and ventral bundles begin in segment ii, and are of 
the same form. They are moderately stout, have the usual double curve, and are bifid 
distally ; the proximal prong of the fork is shorter and stouter than the distal (about 
_ three-quarters as long, and one and a third times as thick at the base); the nodulus is 
distal to the middle of the length of the shaft (proximal : distal :: 3 : 2, or thereabouts). 
The length of the setze in the anterior part of the body is about 115m, but posteriorly it 
is less, the average being about 80u. The number of set per bundle is six, seven, or 
eight in the anterior part of the body, diminishing to three or four posteriorly. 
In the first few segments the prongs of the fork may have a slightly different 
