380 i:. J. ALLEN AND K. VV. NKLSON. 



a. "Tank water" sterilised and treated witli animal 

 charcoal. 

 As F, only growth will be slightly greater and will 

 last considerably longer. Third best in series. 

 H. ''Tank-water" treated with animal charcoal and filtered 

 through Berkefeld filter. 

 This will usuall}^ be the second best culture in the 

 series, but the difference between this and G will 

 only be slight. 

 K. "Outside water" treated with H^O^. 



This will most resemble f, but will not be quite so 

 good. 

 L. " I'ank- water " treated with HoO.,. 



A distinct improvement over k. This medium is 

 rather variable, and in some cases the growth 

 obtained has been quite equal to f, if not better. 



B. Experiments with a View to Determining the 

 Conditions which underlie the Successful 

 Culture of Diatoms. 



The attempt to make cultures of diatoms for use as food 

 when rearing pelagic larvae, led naturally to an effort to 

 determine the best culture medium antl the most favourable 

 conditions for the rapid and continuous growth of diatoms. 

 Before success can be attained in this direction exact know- 

 ledge as to the nature of the essential food-stuffs, and, in 

 fact, as to the general physiology of the Diatomacege, is 

 necessary.^ Numerous experiments, extending over the last 

 three years, have been carried ou»", with a view to obtaining 

 such knowledge, and the results, though still by no means 

 complete or conclusive, are perhaps Avorth recording. 



A great difficulty which has to be met in carrying out such 

 investigations on marine diatoms, is caused by the fact that 

 when sea-water is used as a basis for the culture media, we 



' For general references to literatiu-e see " Bil>liographj-," especially 

 Miqnel (12), Richter (18). 



