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 planorlis 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 Rissow. From the cells of Membranipora pilosa in- 

 crusting the branches of the seaweed, the bodies and tentacles 

 of the pretty polyps protrude. Gampanularia verticillata and 

 C. voluhilis expand their delicately baiTed arms over the 

 transparent cups — now conti-acting as prey is seized, or in- 

 stantly if touched, and again gently unfolding. HippotJwa 

 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 lotnjoides) tuft the tips of others, while in the 

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

 Leptodinum is seated. Pedicellina echinata here and there 

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

 Dr. J. Reid. When irritated the heads bend so as to toucli 

 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 Oldia on agitation of the water. 

 In the pool swim Htppolyte varians and H.pusilla, sessile-eyed 

 crustaceans, and Mysida: ; but the latter are not common in 

 pools north of the pier, apparently giving place in this 

 stormy region to Hippolytai. Besides the ubiquitous shore 

 crab, each pool is inhabited by a spined Gottus, 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 afibrd an ample field for tlie 

 perforations of Pholas crispiata, Saxkava rugosa, and Leuco- 

 dore ciliata. The fissures and chinks of the rocks, more- 

 over, as on almost eveiy part of the Britisli shores, give 

 shelter to a large number, especially the annelids, wliich find 



