ON THE ARTIFICIAL CULTURE OF MARINE PLANKTON ORGANISMS. 441 



An analysis of 1 cc. Miquel sol. B, the amount added to 1 litre Miquel 

 sea- water, gave : — 



PoOg -00825 grill. 



Fe.^Og -0105 „ 



Cab 0145 „ 



Comparing these figures, it seems probable that, when added to sea- 

 water, all the iron in sol. B is precipitated, and a certain amount also 

 of the phosphate and calcium. The additive effect on the sea-water is 

 therefore a slightly increased concentration of phosphate and calcium. 



An analysis of a sample of tank-water for phosphorus, before and 

 after treatment with sol. B (1 cc. per thousand), gave the following 

 figures : — 



Tank-water . . . -5 mgriii. P per litre = -00163 grm. PgO^ 



Tank-water + sol. B 



(without precipitate) . 1-5 ,, ,, ,, =-00488 „ ,, 



It will be noticed that the figures from the different analyses do not 

 agree very well. This is probably due to the fact that different 

 samples were used for analyses in each case, and also to the fact that 

 the solutions were made up in the ordinary way, without any special 

 precautions, volumes, for instance, being measured in cylindrical 

 glasses, pipettes, etc. 



Cultures were tried in sea-water containing the normal amount of 

 sol. A, plus the normal constituents of sol. B, less all the iron and 

 less the amount of phosphate that would combine with the iron to 

 form basic ferric phosphate (P2052Fe203l2HoO). This solution 

 should have very nearly the same chemical composition as normal 

 Miquel sea-water from which the precipitate has been removed. 

 Successful cultures could not, however, be obtained in it. Neither 

 could cultures be grown in sea- water to which had been added the 

 normal amount of sol. A and 1 mgrm. P (as sodium phosphate) 

 per litre. 



To ascertain the effects of the different constituents of sol. B, 

 experiments were carried out with separate solutions of these con- 

 stituents, each of the same strength as in Miquel's formula. Different 

 combinations of these solutions were added, together with sol. A, to 

 sterilized sea-water, and the resulting media were inoculated in the 

 usual way. It was found necessary to repeat these experiments a 

 great number of times, as the results obtained were rather contra- 

 dictory. To illustrate the methods used, a list of the different media, 

 and notes on the cultures obtained in them, are given below. These 

 media were inoculated from cultures of Thcdassiosira dccipicns, and the 



