CULTIVATION OF DIATOMS. 5 1 



After filtration, this "soup" was preserved in sealed tubes. Later on again, 

 he added to his solution some bone gratings, which he said dissolved rapidly 

 in the liquid. At other times he added some well-washed grass roots. 



Although the Gill-solution contains considerably less ingredients than 

 that of Dr. Miquel, and more especially as the salts of magnesium and iron 

 are absent from it, Mr. Gill found that it was quite as favourable to the 

 growth of diatoms as that of the learned French bacteriologist. Still 

 later on however, Mr. Gill, who made his cultivations on a very large 

 scale, modified his liquids and made them more like the Miquel-solution. 

 The liquid which he employed during the last year of his life was made 

 up of a mixture of four distinct solutions, as follows : 



Solution i. Crystallised Sodium phosphate (chemically pure) 2 

 Calcium chloride ( ,, ,, ) 4 



Syrup of Iron chloride ( ,, ) 0-5 



Strong solution of Hydro- 

 chloric acid ( ,, ,, ) i"o 

 Water ... ... ... ... ... ... 100 



Solution 2. Crystallised Magnesium sulphate (chemically pure) 4 



Sodium sulphate ( ,, ,, ) 4 



Potassium nitrate ( ,, ,, ) 4 



Commercial salt (Sodium chloride) ... ... 8 



Potassium bromide ... ... ... ... o - 2 



,, iodide ... ... ... ... ... o - 2 



Water ... ... ... ... ... ... 100 



Solution 3. Crystallised Sodium carbonate (chemically pure) 4 

 Water ... ... ... ... ... ... 100 



Solution 4. Well-washed precipitated Calcium silicate ... 25 



Water 75 



Three cubic centimetres of these liquids are taken and a litre of 

 drinking water or sea water (according to the circumstances of the case) 

 is added to them ; the mixture is well shaken and is portioned out in 

 conical flasks (Erlenmayer's vessels) of ico to 200 c.c, which are filled to 

 a height of about three centimetres. 



The flasks, stoppered with cotton wool, are sterilised either in the oven 

 or by making the liquid boil. The flasks should be allowed to rest for 

 a week at least before planting them with diatoms. 



Solution No. 3 has a double action ; in the first place, it destroys 

 the acidity of the liquid and then precipitates half of the calcium 

 in the form of useful carbonate, for Mr. Gill considered that it 

 was advisable that the diatoms should have at their disposal some 

 solid matter on which they could live and subsist. 



