i] THE CATEGORIES OF LIFE 15 



animals still living in the abysses, for no form of 

 fishing gear yet used would enable us to capture a 

 very large abyssal animal, and one may perhaps 

 still attach some consideration to stories of sea- 

 serpents. Nevertheless the general experience is 

 that the animals obtained from the great depths 

 of the sea are as a rule smaller than their shallow 

 water allies. There is, of course, much that is strange 

 in the abyssal Benthos, but though a zoologist accus- 

 tomed only to shallow water animals would fail to 

 recognise most of the deep-sea forms, he would still be 

 able to refer them to their respective families or classes. 

 Deep-sea animals have certain general characters. 

 Most of the great invertebrate groups, the molluscs, 

 Crustacea, sponges, echinoderms, alcyonarians, etc., are 

 represented in the deep. The Crustacea are often 

 long-legged creatures coloured a uniform red. Most 

 of them are smaller, or at least no larger than are 

 the shallow water forms, but some are relatively 

 gigantic one of the Isopods, for instance, a group 

 represented by the little 'slaters,' is about nine 

 inches in length. Some of the crinoids, tunicates 

 and alcyonarians (seapens) are carried on long stalks 

 apparently an adaptation to life in the soft oozes. 

 There are echinoderms, starfishes and sea-urchins 

 which do not differ in any essential respect from 

 those living in shallow water except that spines are 

 rather more pronounced in the abyssal forms. 



