ABUNDANCE OF PLANKTON 163 



out to what groups of animals his catch belongs. 

 In order to find the real names of animals, or to learn 

 something of their structure and life-history, the reader 

 must consult the ordinary textbooks and special 

 memoirs cited. The figures in most cases have been 

 a good deal simplified from their originals. 



None but zoologists appreciate the wealth of animal 

 life in what appears to be clear, barren sea water. 

 When one realizes that the Right Whale, 50 feet long, 

 lives solely on Plankton, it is easy to see that, as the 

 Prince of Monaco pointed out many years ago, ship- 

 wrecked sailors adrift on boat or raft need never starve, 

 if provided with a simple muslin net. Most groups of 

 invertebrate or backboneless animals are represented 

 in Plankton, and the main types which are likely to 

 be captured at or near the surface will now be sketched 

 briefly, but, it is hoped, sufficiently to enable anyone 

 to ascertain the group to which a specimen belongs. 

 The exact position in the Animal Kingdom of each 

 form named will be found in the classification (p. 430) . 



Animals are divided into two great subkingdoms, 

 according as they are composed of a single cell (Pro- 

 tozoa), or of many cells (Metazoa). 



Of the single-celled animals several groups occur in 

 Plankton, and are distinguished for great beauty and 

 interest. Those which form a skeleton of lime (the 

 Foraminifera) are often represented in warm and tem- 

 perate seas. The shell, into which the animal can be 

 completely withdrawn, consists of successive chambers, 

 generally more or less spirally arranged, opening by a 

 mouth from the largest chamber, and also perforated 

 all over by fine holes. From the chambers radiate 

 extraordinarily delicate spines of lime, which not only 

 help to prevent the animals from sinking by increasing 

 the frictional resistance to the water, but also allow 



