ARTIFICIAL C;iLTUKE 01' MARINE PLANKTON ORGANISMS. 3G9 



Solution 2. 



Crystallised magnesium sulphate 

 Crystallised sodium sulphate . 

 Crystallised potassium nitrate 

 Common salt (sodium chloride) 

 Potassium bromide . 

 Potassium iodide 

 Water ..... 



4 grm. 



4 

 4 

 8 



0-2 „ 



0-2 „ 



100 „ 



Solution 3. 



Crystallised sodium carbonate 

 Water .... 



4 grm. 



100 



Solution 4. 



Well-washedj precipitated calcium 



silicate . . . . .25 grm. 

 Water 75 ,, 



All the salts employed must be chemically pure. Three 

 c.c. of each of these liquids are added to 1000 c.c. of fresh 

 water or sea-water (according to circumstances), and the 

 whole sterilised. In his earlier work Houghton Gill added a 

 sterilised infusion of grass or of diatoms, but it is not clear 

 from the accounts whether this was still employed with the 

 above solutions. We have obtained very good cultures with 

 the above solutions, to which we did not add any organic 

 infusion. 



3. (a) Modification of Miquel's Method: "Miquel 

 Sea-water." — Since several of the components in MiquePs 

 formula for solution A (p. 363) are obviously unnecessary 

 when sea-water is being used as the basis of the culture 

 medium, we adopted for our own work the following modifica- 

 tions : After some preliminary experiments it was found, 

 as would be expected from the composition of sea-water, 

 that the only salts of value to the medium are the three 

 nitrates KNO3, NaNOs, NH^NOg, and possibly KBr and KI. 

 The omission of the two latter was soon found to make no 



