34 THE SOCIAL LIFE OF ANIMALS 



be no attempt to catalogue all known instances or 

 to select merely the very best cases known. I shall 

 try to use examples that are not too shopworn by 

 repeated description. 



Almost every observant person has seen the soft 

 green "bloom" which covers many stagnant ponds. 

 Under the microscope this "bloom" is often seen to 

 be composed of myriads of the tiny plant-animal 

 Euglena. These organisms are commonly one-tenth 

 of a millimeter long, which means that in a char- 

 acteristic layer of "bloom" there would be at least 

 sixty to one hundred thousand animals per square 

 inch; and acres of water are sometimes covered. 



Lobster-krills are small crustaceans that occur com- 

 monly in shoals about the Falkland Islands, Pata- 

 gonia, New Zealand and other southern waters. (81) 

 A larval stage of this animal, less than an inch long, 

 occurs often on the surface of the water in such 

 numbers that the sea is red for acres; and whales in 

 those waters simply open their mouths and swim 

 through slowly, feeding with no more effort than 

 the process of straining them out. These shrimp- 

 like animals may be piled up on the shore by tide 

 and wind in stench-producing layers. Dampier wrote 

 of them in 1700: "We saw great sholes of small lob- 

 sters, which colored the sea red in spots for a mile 

 in compass"; and they have been known to extend 



