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 colour, wonderful 
structure and habits, they are not surpassed by any invertebrate 
class. The splendid bristles of the Aphroditidm, constantly 
glistening with all the hues of a permanent rainbow, the bril¬ 
liant colours of the Phyllodocidm, Hesionkhe, and Nereidse, and 
the gorgeous branchial plumes of the Terebellidse, the Sabel- 
lidse, and the Serpulidse 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 structural 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 surroundings; 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 
