i8o BRITISH FISHERIES 



the sea off Helgoland. The method thus initiated 

 was prosecuted by Huxley, Haeckel, Vogt, Gegen- 

 baur, and a host of others/ and at the present day 

 it is employed by every marine naturalist. In all 

 questions and studies belonging to marine biology or 

 economic fisheries research, the study of the plankton 

 becomes indispensable at some stage or other. 



Generally speaking, there are two principal 

 points of view from which the study of the fauna 

 and flora of the sea can be approached. The 

 latter form a vast storehouse of biological material 

 on which the systematic biologist, or the investi- 

 gator who concerns himself with the identification 

 and recording of species of plants and animals, 

 can draw at will. Then there are the life- 

 histories of marine organisms to be studied ; and 

 in the plankton we meet with stages in the 

 development of nearly all marine organisms, so 

 that the latter is a great storehouse of material 

 for the comparative embryologist. An excellent 

 sample of this latter kind of work is to be found 

 in the researches on the life-histories of the British 

 marine fishes carried out by M'Intosh and the 

 St Andrews school of zoologists ; but an enormous 

 number of such investigations have been carried 

 out in all civilised countries. The distribution of 



' See Haeckel, Plankton-Studien, G. Fischer, Jena, 1885 (or the 

 EngHsh translation in the U.S. Fish Commissioner's Report for 

 1889-91, Washington, 1893), for a historical account of plankton 

 investigations. 



