440 ON THE ARTIFICIAL CULTURE OF MARINE PLANKTON ORGANISMS. 



action of Miquel's solutions, for no increase in growth is obtained when 

 nitrates or sol. A only are added to sea-water. To illustrate this point 

 an account of an actual experiment may be given : — 



Inoculated with Thalassiosira declpiens. 



A. Normal Miquel sea-water. 



Good strong culture, in every way normal. 



B. Outside water sterilized. 



Small growth at first ; very soon exhausted. 



C. Ditto -I- sol. A. 



No improvement over B. 



D. Ditto + sol. B. 



Fair groAvth. Great improvement on B and C, hut exhausted 

 considerably before A. 



E. Tank-water sterilized. 



Appreciably better than B, but growth not large. 



F. Ditto + sol. A. 



Not even as good as E. 



G. Ditto + sol. B. 



Next best in series to A ; lasted longer than D, and had l^etter 

 coloiu'. 



To generalize, no improved culture is obtained with sol. A alone, 

 but a fair, though not very lasting, growth can result from using 

 sol. B only. 



The action of sol. B is to some extent obscured by the fact that, 

 when this solution is added to the alkaline sea-water, a precipitate 

 is formed. This precipitate is at first white, but, on heating or stand- 

 ing for some time, it becomes greenish yellow. We are indebted to 

 Mr. D. J. Matthews for the following analyses. 



Ten litres of normal Miquel sea-water were prepared, and the pre- 

 cipitate was collected on a filter paper washed and dried at 100° C. 



Weight of dry precipitate from 10 litres = 0*2949 grm. 



100-16 



Or, the precipitate from 1 litre of normal Miquel sea-water contains : — 



P2O5 -00777 grm. 



FePg ...... -01218 „ 



CaO -00225 „ 



