[ 417 ] 



On the Culture of the Plankton Diatom Thalassiosira 

 gravida Cleve, in Artificial Sea-water. 



E. J. Allen, D.Sc, F.R.S., 



Director of the Plymouth Laboratory. 



In a former paper,* written in conjunction with my colleague Mr. E. W. 

 Nelson, the conditions under which a rapid and continuous growth of 

 marine plankton diatoms can be obtained in laboratory cultures were 

 discussed. It was pointed out that when natural sea- water is used as the 

 basis of the culture media we are dealing with a solution of a very complex 

 and variable character, the exact nature of which it is extremely difficult 

 to determine, and that the ideal to be aimed at is to find a culture medium 

 with artificially prepared sea-water as its basis, such that the absence or 

 diminution in quantity of any one of its constituents would have a pro- 

 found effect upon the growth of diatoms in it. A reference was made 

 {he. cit., p. 446)'|" to some experiments with artificial sea- water, which, 

 whilst pointing to the probability of successful work being possible on 

 these lines, were in themselves too uncertain to be satisfactory. 



Experiments in this direction have been continued at intervals during 

 the past three years, and although the problem has not been completely 

 solved the results obtained seem to be of sufficient interest and import- 

 ance to warrant publication in their present incomplete form, more 

 particularly because points remaining to be cleared up probably require 

 a knowledge of the chemistry of organic compounds to which I cannot 

 lay claim. 



Stated in general terms the most interesting result so far obtained is 

 that in the artificial sea-water tried, made by dissolving Kahlbaimi's 

 pure chemicals in doubly distilled water, little or no growth of diatom 

 {Thalassiosira gravida Cleve) takes place, but if to this artificial sea-water 

 as little as 1 per cent of natural sea-water is added vigorous and large 

 cultures are obtained, and wdth an addition of about 4 per cent of 



* Allen, E. J., and Nelson, E. W. "On the Artificial Culture of Marine Plankton 

 Organisms," Journ. Mar. Biol. Assoc, VIII, 1910. Also in Quart. Jouni. Micr. Set., 

 Vol. LV, 1910. The two papers are identical. 



t Q.J. M.S., Vol. LV, p. 393. 



NEW SEHIES. — V<JL. X. NO. 3. OCTOCEIt, 1914. 2 D 



