316 DECEMBER. 



and described in this series of essays. However, as they 

 are the lowest, so shall they be the last ; for, with a few 

 notes on some of our species, I shall dismiss my kind 

 and courteous readers. 



The inferior surface of this huge slab of limestone, 

 supported at one end by a boulder, while the other end 

 is imbedded in the mud or concealed by the smaller 

 fragments that are thrown in confusion around, is 

 densely studded with organisms. It is only at very 

 low tides that this arch is exposed, though now we can 

 creep in and work with no great discomfort, though 

 with some defilement of our garments from the mud 

 and slime. The absence of direct light is favourable to 

 the growth of marine productions, and thus we have 

 another congenial element in the obscurity. With some 

 of the smaller sea-weeds, chiefly of the filamentous 

 kinds, as Cladoplwra, Conferva, some of the minuter 

 Callitkamnia, etc., the majority of the forms that crowd 

 and cover the rock so densely are animals : indeed 

 there are large areas where the animate forms struggle 

 so perseveringly for standing-room, that not a filament 

 or frond of vegetation can be seen, and you could not 

 thrust the point of a penknife down to the rock in any 

 spot without wounding some or other of the incrusting 

 creatures. Polyzoa are here, chiefly of the tufted 

 species ; Hydrozoa, too, hang down ; Anemones, but 



