SALPA IN RELATION TO EVOLUTION OF LIFE. 135 



a vast array of dark-browii jelly-fishes (Linerges raercutia), whose 

 dark color made them very conspicuous in the clear water. They 

 were not densely crowded, although they were so abundant that 

 nearly every bucketful of water we dipped up contained some of 

 them. We could see them at a distance from the vessel, and at 

 noon, when the sun was overhead, we could look down into the 

 water to a great depth through a well in the middle of the vessel 

 where the centreboard hung, and as far down as the eye could pene- 

 trate, fifty or sixty feet at least, we could see the brown spots drift- 

 ing by like motes in the sunbeam. We cruised through them for 

 more than five hundred miles, and we tacked back and forth over 

 a breadth of almost a hundred miles, and they were everywhere in 

 equal abundance. 



The recent literature of pelagic exploration, which has been sum- 

 marized by Haeckel (Plankton Studien : von Ernst Haeckel, Jena, 

 1890), is full of references to great accumulations of pelagic animals, 

 from which I have selected those which follow. 



Chiercha says that during a cruise of forty days between Peru 

 and Hawaii the net brought in from the surface and from all depths 

 down to about two miles, a multitude of pelagic animals which 

 would be incredible to those who have not witnessed it. 



The naturalists of the Challenger found the waters of the equa- 

 torial Pacific swarming with life, not at the surface alone, but in 

 its deeper layers, and the ship often sailed through great banks of 

 pelagic animals. 



The equatorial Atlantic is like the Pacific, and Chiorcha says 

 that its zone of equatorial calms is rich beyond all measure in animal 

 life, and that the water often looks and feels like coagulated jelly. 



Of the Indian Ocean, Haeckel says that in his voyage to and 

 from Ceylon he was wonderstruck with the wealth of pelagic life 

 day after day on the mirror-like surface. At night it was an un- 

 broken sheet of sparkling light as far as the eye could reach, and 

 the water which was dipped up at random held such a thick swarm 

 of densely crowded luminous animals (Ostracods, Salpse, Pyrosoraas, 

 and Medusae) that a printed book could be read distinctly in a dark 

 night by this pelagic light. 



In temperate and arctic waters there is less diversity, but, as 

 Haeckel shows, there is no evidence of any decrease in individuals, 



