100 MARINE FAUNA OF ST. ANDREWS. 



Class ANNELIDA. 



The marine annelids have sometimes been considered an un- 

 inviting group, dimly associated with parasites and earthworms. 

 In regard, however, to beauty of form and coloui-, wonderful 

 structm-e and habits, they are not surpassed by any invertebrate 

 class. The splendid bristles of the Aphroditidte, constantly 

 glistening with all the hues of a permanent rainbow, the bril- 

 liant colours of the Phyllodocidfe, Hesionidffi, and Nereidaj, and 

 the gorgeous branchial plumes of the Terebellidaj, the Sabel- 

 lidffi, and the Serpulidae can only be compared with the most 

 beautiful types of butterflies and birds. The structures formed 

 by many exhibit an amount of precision and skill equal to 

 that of the most remarkable insects. Thus, at St. Andrews, 

 the common Pectinaria belgica fashions a tube like a straight 

 horn of minute pebbles, carefully selected and admirably fixed 

 to each other by a whitish cement. In the placing of these 

 together there is no haphazard, but angle fits angle as 

 in a skilfully built wall, and no profusion of the whitish 

 cement hides slovenly masonry. There is much similarity 

 in the ordinary tubes ; dozens may be examined without 

 observing any noteworthy sti'uctural difference. All have 

 the same blending of the white or light-coloured grains 

 with the yellow, the brown, and the black. There is no 

 chance grouping, so as to cause the tube to be out of harmony 

 with its suiToundings ; but the whole tone is such that it can 

 with difficulty be distinguished from the sand. Some annelids, 

 again, secrete transparent tubes of the aspect and toughness 

 of crow-quills ; while others cement the mud into caoutchouc- 

 like pipes, fix gravel, stones, and shells by the same means 

 into convenient tunnels, or rely on the parchment-like tenacity 

 of a tube formed solely of one or more layers of their re- 

 markable secretion. The interest in the group is further 

 heightened by the brilliant phosphorescence characteristic of 

 many, and the powers which others have of perforating 



