i 3 4 THE POPULAR SCIENCE MONTHLY 



is demanded by the logic of the law of evolution. But just what they 

 feel and to what degree they think is largely unknown. In the solu- 

 tion of these fascinating problems enduring biological research will give 

 us knowledge where metaphysical speculation has left us groping and 

 fencing with a jargon of terms. 



Among the general problems to be solved in marine stations none 

 are more interesting than those concerning the countless millions of 

 organisms, that float in the surface waters as the plankton. Professor 

 Theel has investigated these matters in the neighborhood of Fiske- 

 backskil since 1874 and has published important conclusions as to the 

 origin and fate of the plankton. While most of these organisms consti- 

 tute the holoplankton, always swimming freely, yet many, especially in 

 the breeding season, belong to the meroplankton, swimming as larvae 

 only part of the time and then going to the bottom to form the ben- 

 thon population, or to become anchored for the rest of life like the 

 corals. One mystery at Kristineberg is that while many chsetopod 

 worms live in the bottom ooze their swimming larvas appear but rarely 

 in the plankton. On the other hand some forms occur at times in such 

 masses as to make the water thick. Here, as on other seashores, the 

 phosphorescent protozoan Noctiluca miliaris has been cast up in win- 

 drows of glowing greenish blue living fire. This tiny creature, in com- 

 mon with many other organisms, emits light when touched or rolled 

 about, or upon chemical or electrical stimulation. It is possible on a 

 dark night to read by their phosphorescence, Avhich after all is but a 

 secretion of their photoplasm on fire. 



In the bay near Kristineberg from 1890 to 1900, the irregular sea- 

 urchin Echinocardium cordatum occurred in large numbers but in the 

 summer of 1902, none of the adults were found and only the young of 

 •one centimeter, or less, in size. It is the view of Professor Theel that 

 in such cases, during some unfavorable years, the currents of the sea 

 bear the swimming larvas away from the ancestral breeding ground 

 where, during their metamorphosis, they may be eaten by hungry 

 hunters, or else sink in the abysmal waters and perish. If they find 

 favorable bottom they will there establish a new race while the old un- 

 replenished parent stock dies out. Thus in 1902 new larvas of Echino- 

 cardium came to Kristineberg bay and reestablished the colony in its 

 former home. 



So animals appear and flourish in a region only to die out, while 

 others come in to take their places. The rise of the herring fishery in 

 these waters within the last forty years has seen the decline and prac- 

 tical extermination of the oyster business. In view of the fact that the 

 planktonic larvas, while free-swimming yet depend upon the sea-cur- 

 rents to place them upon the right bottom, it is no wonder, that many 

 perish in the constant struggle for existence. It is only because of the 



