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 Skenea 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 Mevibranipora pilosa in- 

 crusting the branches of the seaweed, the bodies and tentacles 

 of the pretty polyps protrude. Campanularia verticillata and 

 C. 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. Hippotkoa 

 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 (Lezt- 

 cosolenia botryoides) tuft the tips of others, while in the 

 vantage-ground afforded by a fork of the seaweed a colony of 

 Leptoclinum is seated. Pedicellina echinata here and there 

 attracts notice — some of the stems headless, as described by 

 Dr. J. Keid. 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.pustlla, 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 Hippolytw. 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 Pholas crisjyata, 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 



