THE SEA LEMON. 59 



is still at a great elevation above the sea-level ; and 

 when we have made our way to its sea-ward margin, 

 and look down upon the pebbly beach, we find that 

 we can reach it only by a- narrow zigzag path, or 

 almost a succession of narrow steps, so steep and 

 hazardous that the utmost circumspection is necessary 

 to descend it with safety. 



Once down, we can walk along the rough platforms 

 and ledges of sandstone that extend along at the foot 

 of the lofty cliffs towards the north from the cove. 

 The strata form narrow shelves with sharp edges, 

 sufficiently level to be traversed without difficulty, 

 but gradually rising from the horizontal, so that we 

 cannot pursue any given stratum beyond a short 

 distance, as we find it carrying us too far above the 

 sea, but must successively descend to lower ones. 



In the crevices and shallow pools of the ledges 

 between tide-marks I observed numerous colonies of 

 Actinia hellis, a variety more than usually pied with 

 white on a dark ground: and the fine A. crassicornis 

 was common in the darker fissures. It was here that 

 I saw for the first time the largest of our naked-gilled 

 Mollusca, the Sea Lemon, Doris tuherculata. It was 

 lying in a narrow horizontal shelf under the shadow 

 of a rock, whence it had doubtless fallen after it had 

 been forsaken by the tide. My first momentary 

 impression was that a large limpet had been extracted 

 from its shell and thrown there to die, but an instant's 

 examination told me what it was. I carried it to a 

 shallow pool and threw it in; and presently it turned 

 itself on its foot, and protruding its two curiously-rib- 

 bed tentacles from their holes, began to glide along 



