PELAGIC PLANT LIFE 311 



has further, by his quantitative investigations of the variations in 

 the plankton of Kiel Bay and off Syracuse, taught us the value 

 of exact studies of this description. 



Our future investigations will have to be conducted on three 

 main lines : — 



(i) In the first place, much study must be devoted to the 

 biology, in the restricted sense of the word, of the algae. We 

 will have to learn how the forms adapt themselves to their 

 conditions of life, and in particular to their floating existence. 

 Here, however, a great advance should most certainly be made, 

 now that W. Ostwald has shown us a new factor affecting their Ostwaid. 

 floating power, namely, the varying viscosity of sea-water, and 

 since the instructive writings of Wesenberg-Lund have directed Wesenberg- 

 our attention to the seasonal modifications which the species ^""^• 

 adopt to suit variations in viscosity. 



(2) In the second place, the distribution of the species 

 throughout the seas of the world requires further investigation 

 at different seasons, and this must be founded on a careful 

 characterisation of the different species. In recent years the 

 peridineae, after a long period of neglect, have received due paviHard 

 attention at the hands of Ostenfeld, Ove Paulsen, Pavillard, jorgensen. 

 Jorgensen, Broch, and Kofoid. A great deal, however, still Broch. 

 remains to be accomplished. Kofoid. 



(3) In the third place, we will have to deal with the laws of 

 production in the sea. This great physiological question calls 

 for observations on a very comprehensive scale, if we are to be 



in a position to discuss the interesting theories put forward by ^^^^^^^ 

 Brandt, Nathansohn, and Putter. A brief discussion of their Nathansohn 

 theories will be found at the end of this chapter. piuter. 



During the Adantic Expedition of the " Michael Sars " we 

 were able to make observations on all these three aspects of 

 the subject ; and in what follows I shall endeavour to summarise 

 our results, and to consider, while doing so, the attitude at 

 present taken up by the scientific world with regard to these 

 three lines of investigation. 



Most of the ocean plants exist in countless myriads of General bio- 

 minute individuals, though they are invisible to the naked eye. p°e^g°c aiga. 

 Still, small as they are, they are in a way highly organised, 

 and their organisation is in strict accordance with the particular 

 conditions of life. On land' a higher plant consists of a 

 community of separate cells, each of which has a special function 

 to perform in the service of the whole. It establishes an under- 



