62 THE SEAS 



sea weed, and has roots for absorbing nutriment from the 

 soil. In some parts of the Kattegat and in the lagoon-like 

 Limfjord in Denmark, it covers vast areas. The associated 

 fauna is not very rich ; a little snail called Rissoa is very 

 plentiful and thib is also the haunt of the beautiful green 

 Haliclystis best defined as a little, squarish jellyfish, which 

 crawls about on the eelgrass. This is the home of fish 

 such as sticklebacks and pipe-fishes, the latter, which have 

 long, slender, brown or green bodies, being very difficult to 

 see against the dead and Uving blades of eelgrass. They 

 swim in an upright position by the vibration of the delicate 

 dorsal fin, coming to rest in the same position and swaying 

 with the motion of the water. Closely related to them is 

 the quaint sea horse. A number of snails lay their egg 

 capsules on eelgrass, on which, however, there are few 

 encrusting animals. 



A large and characteristic fauna is found on hard bottoms 

 in the Littoral zone. There are many attached animals, 

 notably sponges, sea mats, hydroids, sea squirts and corals, 

 the latter including " Dead-men 's-fingers " [Alcyonium 

 digitatimi), consisting of dead-white, finger-like growths 

 covered with tiny pol3^ps (Plate 23), and the little solitary 

 coral, Carj'ophyllia, which is almost our only example of 

 a true " stony " species. Serpulid worms, which live in 

 limy tubes and have little plugs for closing the opening 

 when the plumose tentacles are withdrawn on the approach 

 of an enemy, are common and also a variety of molluscs 

 like the saddle-oyster, whelk, chiton and, of special interest, 

 the delicate bivalve, Lima hians. This has a fringe of long 

 orange tentacles which cannot be withdrawn within the 

 shell, but float in the water and make it the most beautiful 

 of bivalves. It has the interesting and very unusual habit 

 of living in a nest which it constructs out of pieces of stone 

 and shell bound together with fine threads. Sea urchins are 



