174 THE OCEAN RIVER 



similar studies into all parts of the oceans, but even today 

 marine biological research is at least as active along the At- 

 lantic shores and in the waters of the River as elsewhere. 



This salty cradle of life has been dominated by a procession 

 of very different kinds of living creatures, so that there have 

 been at various times an Age of Trilobites, an Age of Squids, 

 and an Age of Reptiles. Today is a new Age of Fishes, which 

 began when fishes displaced the swimming reptiles and in- 

 herited the ocean. Nevertheless, throughout all the ages there 

 has continually flourished another and lower stratum of 

 marine life without which the larger animals could never 

 have existed. Plankton, as it is called, has been throughout 

 these ages the very foundation of life in the sea. Migrations 

 of fishes within the waters of the River and mysterious fluctu- 

 ations in their abundance are influenced directly not only by 

 changes in temperature, saltness, and flow of water, but also 

 by the fluctuations in growth and movement of their plankton 

 food which accompany these changes. Since the plankton 

 consists mostly of small plants and animals without sufficient 

 powers of movement to swim against currents, it is particu- 

 larly dependent on the ocean circulation. It is worth our study 

 for many practical reasons. 



Unseen by travellers who peer overboard into the blue 

 transparent ocean, but coming to life under the lens of the 

 microscope, is a teeming world in miniature, fantastic and 

 infinitely varied, a kind of miniscule botanical garden and 

 zoo, and the very nursery of the ocean. Single-celled plants 

 are fashioned in surrealist design or housed in delicately carved 

 silica capsules. They may have intricately sculptured shapes 

 with long spines, or carry in their bodies decorative oil globules 

 to keep them from sinking. They are in a functional sense both 

 the pasturage and corn land of the sea, for they vastly exceed 

 in total bulk those larger marine plants, the seaweeds, even 

 though plankton organisms themselves are often thousands 

 of times smaller. 



