Seaweeds and Leaf-green 



and so baffles its enemy. The light would probably be 

 just as effective as the searchlights used in the Russo- 

 Japanese war. 



A curious experiment has been recorded which may 

 yet have a practical application. 



One fills an ordinary tumbler one-third full of alcohol 

 (this is more than three-fingers or a third mate's peg, as 

 it is sometimes described), and then adds as much sea- 

 water with pyrocystis in it as it will hold. 



If one then gently shakes or jars the tumbler, the 

 pyrocystis glow with most unusual brilliancy for a time, 

 not exceeding four minutes ; they then sink to the 

 bottom of the tumbler and remain very quiet indeed for 

 a very lengthened period ! 



One must imagine not only these few plankton algae 

 which we have mentioned, but many others developing 

 regularly their one or two harvests, and being greedily 

 devoured by many varied and remarkable marine free- 

 swimming animals. 



There are also the beautiful submarine meadows and 

 thickets of the shore algae. 



The world of fishes feed upon the smaller animals 

 which graze upon the diatoms and other planktons. 



In fresh-water lakes one finds almost as varied and 

 quite as beautiful a series of algae. There are both shore 

 forms and free-swimming plankton. 



In the South of Scotland, the entire bed of a small burn 

 or pond, every submerged stem of pond-weed, and every 

 pebble may be covered with a curious golden-brown 

 or dark brown mistiness. 



One finds under the microscope that this is due to 

 small diatoms attached by delicate and almost trans- 

 parent threads of jelly, and which, when observed in 

 their natural condition, are exceedingly beautiful. They 

 also have regular seasons of development ; some appear 



39 



