INTRODUCTION. 
7 
feet and turn their shells with business-like pertinacity, mean¬ 
while exposing their minute black eyes and feeling in all 
directions. The little SJcenea planorbis can just be distin¬ 
guished with the naked eye as it crawls and twists on the 
seaweed; it is less apt to leave the latter and its native element 
than the Rissoce. From the cells of Membranipora pilosa in- 
crusting the branches of the seaweed, the bodies and tentacles 
of the pretty polyps protrude. Campanularia verticillata and 
G. volubilis expand their delicately barred arms over the 
transparent cups—now contracting as prey is seized, or in¬ 
stantly if touched, and again gently unfolding. Hippothoa 
divaricata , which here (on seaweeds), according to Dr. John¬ 
ston, alters its shape, shoots its delicate white stems from a 
branch of the Ceramium. Masses of the snowy sponge (Leu- 
cosolenia botryoides) tuft the tips of others, while in the 
vantage-ground afforded by a fork of the seaweed a colony of 
LeptocUnum is seated. Pedicellina ecbinata here and there 
attracts notice—some of the stems headless, as described by 
Dr. J. Reid. When irritated the heads bend so as to touch 
the basal portion of the stem or the surface of the seaweed. 
In the deep part of the pool the tangles spring from the per¬ 
pendicular rock and from stones at the bottom—waving their 
rich fringes of phosphorescent Obelia on agitation of the water. 
In the pool swim Hippolyte varians and H.pusilla, sessile-eyed 
crustaceans, and Mysidce • but the latter are not common in 
pools north of the pier, apparently giving place in this 
stormy region to Hippolytce. Besides the ubiquitous shore 
crab, each pool is inhabited by a spined Cottus , whose fine 
iridescent hues of silvery bluish green are displayed most 
vividly in the water. The larval form called Campontia 
eruciformis by Dr. Johnston swarms amongst the roots of 
Corallina in summer, just as another insect-larva does amidst 
the damp and decaying seaweeds on the sand at high-water 
mark, and a third in the muddy fissures of the tidal rocks. 
The soft sandstone and shale afford an ample field for the 
perforations of Pliolas crispata , Saxicava rugosa , and Leuco- 
dore ciliata. The fissures and chinks of the rocks, more¬ 
over, as on almost every part of the British shores, give 
shelter to a large number, especially the annelids, which find 
