THE WONDERS OF LIFE 



looked upon, from the purely physical stand-point, as a 

 result of superficial strain. On the other hand, the 

 physiological character of these plasmodonious monera 

 is especially iniportant, as it gives us the simple key 

 to the solution of the great question of spontaneous 

 generation (or archigony, cf. chapter xv.). 



The chromacea are to-day found in every part of the 

 earth, living sometimes in fresh water and sometimes 

 in the sea. Many species form blue-green, violet, or 

 reddish deposits on rocks, stones, wood, and other 

 objects. In these thin gelatinous plates millions of 

 small homogeneous cytodes are packed close together. 

 Their tint is due to a peculiar coloring matter (phyco- 

 eyan), which is chemically connected with the substance 

 of the pla§mavparticle. The shade of this color differs 

 a good deal in the various species of chromacea (of 

 which more than eight hundred have been distinguished) ; 

 in the native species it is generally blue^green or sage- 

 green, sometimes blue, cyanine blue, or violet. Hence 

 the common name cyanophyceae {i.e., blue algae). It is 

 incorrect, for two reasons ; firstly, because only a part of 

 these protophyta are blue, and, secondly, because they 

 (as simple, primitive plants without tissue) must be 

 distinguished from the real algae (phyceae), which are 

 multicellular, tissue-forming plants. Other chromacea 

 are red, orange, or yellow in color, as the interesting 

 triehodesmium erythrcBum, for instance, the flaky masses 

 of which, gathering in enormous quantities, cause at 

 certain times the yellow or red coloring of the sea-water 

 in the tropics; it is these that are responsible for the 

 name "Red Sea" on the Arabian and "Yellow Sea" on 

 the Chinese coast. When I passed the equator in the 

 Sunda Straits on March lo, 1 901, the boat sailed through 

 colossal accumulations, several miles in width, of 

 this triehodesmium. The yellow or reddish surface of 

 the water looked as if it were strewn with sawdust. 



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