THE BRISTLE-WORMS. Ill 



worm not infrequently throws off these filaments, which 

 retain their activity for a long time, and often greatly 

 puzzle the beginner. This worm is Cirratulus cirratus, and 

 is often exceedingly common in black sand or mud under 

 stones. In the early part of the year the worms quit the 

 mud, and may be found freely exposed on the rocks in the 

 act of spawning. The eggs are of yellowish colour, and as 

 in most worms are surrounded by a jelly-like substance. 

 As in the case of not a few littoral animals, it is only at 

 the breeding season that one is able to get any adequate 

 idea of the extraordinary number of individuals which 

 occur between tide-marks. In the Firth of Forth in Feb- 

 ruary I have seen the rocks literally covered with the 

 worms, while at other seasons they can only be found by 

 careful search. 



It is not necessary to say much of the characters of the 

 worm. The prostomium is long and pointed. Behind it is 

 a transverse row of tentacular filaments, which in life are 

 distinguished from the gills by their paler colour and their 

 "curled" appearance. After death it is not easy to dis- 

 tinguish between gills and filaments. The gills are of 

 course modified dorsal cirri. They are long, slender, and 

 filamentous, and the colour is bright red. They are- most 

 numerous and most regularly arranged on the anterior 

 segments; but scattered gills occur throughout the greater 

 part of its length. Apart from the gills, the parapodia are 

 merely represented by papillae at each side of the segments 

 bearing small bristles. On the East Coast at least the worm 

 does not usually exceed three to four inches in length. 



Much more interesting than Cirratulus are the Terebellids, 

 or sand-masons, which build long tubes neatly plastered over 

 with particles of sand, shell, and stone. In walking over 

 the sand after the tide has ebbed, one very often finds 

 great masses of the sandy tubes of these worms. Some of 

 these tubes are fringed at the top with branched sandy 

 threads, so curious in appearance that the inexperienced 

 commonly regard the tube as some kind of an animal. 

 These are the empty tubes of TereMla conchilega, the sand- 

 mason, and sometimes occur on the shore in extraordinary 

 abundance. They are always empty, however, and usually 

 not more than a few inches in length. We need not, 



