SURFACE-SWIMMING FAUNA (INVERTEBRATES). 107 



and the debateable particles called Coccospheres 

 and Rhabdospheres, add to the number of the 

 floating Flora of the seas. 



The importance of these organisms to the 

 zoologist is that they must ultimately form the 

 food supply of the animals of the Plankton. 

 Some of the larger animals may feed upon the 

 smaller ones, and the smaller ones may, in their 

 turn, feed upon still smaller ones, but we must 

 come eventually, in descending the scale, to the 

 animals that are vegetable-feeders and prey upon 

 the minute plants that have just been mentioned. 



Now that we have considered very briefly 

 some of the principal forms of life that compose 

 the floating and drifting population of the sur- 

 face, we may return to the subject with which 

 the chapter opened, namely, the phosphorescence 

 of the sea. 



It need hardly be mentioned that it is a sub- 

 ject which is beset by innumerable difficulties. 

 Even when the sea is extremely phosphorescent, 

 and the observer is provided with an excellent 

 microscope and all the necessary scientific appli- 

 ances, he finds it difficult to answer the question 

 "What is the cause of the phosphorescence to- 

 night 1 " The sample of water he takes may 

 reveal to him a multitude of different organisms, 

 many of which are so small that they can only 

 be seen with a strong artificial light, and then it 

 is impossible to say which are and which are not 

 phosphorescent. 



Some of the Copepods are known to possess 

 an organ emitting a bright blue star-like light 

 which shines for a time and is then suddenly ex- 



