THE OCEAN FOOD SUPPLY 333 



Fifteen rich hauls with trawl and dredge in depths varying 

 from 40 to 300 fathoms enabled a large collection of the benthos 

 to be made. A striking feature of the marine fauna of the Ant- 

 arctic is the extraordinary wealth of individuals, while the variety 

 of forms does not appear to be very great. Also the large size 

 to which some species attain as compared with their relatives in 

 warmer seas is very marked. 



This is, however, not the case with animals which require 

 carbonate of lime, for the secretion of limy skeletons by members 

 of the benthos seems to be at a minimum in the cold Antarctic 

 waters. The shells of molluscs are small and fragile. Some sea- 

 snails have no lime in their shells at all. 



It requires the warm tropical seas for anirrials with calcareous 

 skeletons to reach their vigorous growth. 



Many of the bottom animals crawl over the sea floor and pass 

 the nutritious mud through their digestive organs after the man- 

 ner of earth worms; others take up a stationary vertical posi- 

 tion, and by means of tentacles waft the falling diatoms into their 

 mouths before they have time to reach the bottom. 



Almost every trawl brought up quantities of large siliceous 

 sponges covered with glassy spicules. 



Good collections of sea-anemones, worms, urchins, starfishes, 

 Crustacea, sea-spiders, molluscs, and fishes were obtained. The 

 collection of fishes has already been found to contain some new 

 genera and several new species. There can be no doubt that 

 many new forms will be found among the other groups. 



Considerable quantities of three species of Cephalodiscus 

 were obtained. These animals are of interest because they show 

 signs of a distant relationship to the vertebrates, though their 

 mode of life is very dissimilar. The minute individuals live to- 

 gether in colonies, and build up a gelatinous tree-like house. 



The young forms of Cephalodiscus are very imperfectly 

 known, and it is hoped that larval stages may be found among 

 ihe material brought home, so that further light may be thrown 

 upon the development of these curious animals. 



In the last volume of the Biological Reports it is proposed to 

 review the known marine benthos of the continental shelves of 

 the globe in regard to its distribution in time and space. One of 

 the objects of this enquiry will be to ascertain, as far as our pres- 

 ent knowledge will permit, if there has been any tendency on the 



