PELAGIC PLANTS AND FORAMINIFERA. 7 



waters that the abundance and variety of animals are in many 

 respects due, especially if estuaries also debouch in the neigh- 

 bourhood. Thus nowhere are the swarms of Sagittse, Appen- 

 dicularians, Crustaceans, and other groups of fish-food more 

 conspicuous than in the midst of a sea teeming with diatoms, 

 Rhizosoleniae and other algoid structures.' 'Now this plant- 

 life is specially rich in April and May, just when the larval 

 and very young post-larval fishes appear more abundantly in 

 the inshore waters, so that the cycle is nearly complete, viz., 

 from the inorganic medium — through microscopical plant and 

 larval crustacean — to the post-larval fish\' Similar views have 

 been broached by Prof Hensen of the German Expeditions and 

 Dr George Murray of the British Museum ; while Prof Cleve, 

 of Upsala, is of opinion that even the origin of the coastal 

 currents in certain cases may be traced by their diatoms ^. 



Besides, both adult and adolescent marine fishes such as 

 sand-eels devour the green and greyish-green algae of the 

 Eden, even to the distention of their stomachs in May. Algae, 

 again, are not uncommon accompaniments of food in other 

 fishes. 



Broadly speaking, therefore, the sea has within its area a 

 vast and ever-present source of nourishment for its teeming 

 animals — a source altogether independent of the increment 

 from fixed marine vegetation on shore or swept into it by 

 rivers. This supply can in no way be affected by the action of 

 man, who is as powerless to modify it as to modify the tides. 

 So long as it remains, one of the most important factors for the 

 safety of the food-fishes is secured. 



In the ocean are immense numbers of Foraminifera and 

 Radiolarians upon which the lower invertebrates prey both at 

 the surface and the bottom. They in turn feed on diatoms and 

 other simple plants and animals, and thus aid in completing 

 the cycle from plant to fish. The records of the rocks show 

 that many of both groups were as prevalent in the ancient seas 



1 Lecture, Royal Instit. of Great Britain, Friday, February 1, 1889, p. 10. 



2 Dr Petersen, of the Danish Zoological Station, has just issued an interest- 

 ing addition to our knowledge of this subject — from observations in the 

 Limfjord. 



