580 EEPORT OF THE COUNCIL. 



students from Oxford and Cambridge. Dr. Cressvvell Shearer again 

 brought a class of five students from Cambridge for a practical course 

 in Experimental Embryology. 



Mr. E. J. Lewis brought a class of seven boys from Oundle School 

 for practical work during the last fortnight of iipril, and Messrs. J, T. 

 Cunningham and H. B. Lacey, with four students from the South- 

 western Polytechnic, Chelsea, spent Whitsuntide in working at the 

 Laboratory. 



General Work at the Plymouth Laboratory. 



The Director has continued his experimental investigations into the 

 conditions of growth of marine plankton diatoms. Several of the latter 

 can now be cultivated in almost entirely artificial solutions prepared 

 from the purest chemical salts obtainable, and in this way an oppor- 

 tunity is afforded for studying directly the effect of minute changes in 

 the composition of the medium in which these diatoms live. It is hoped 

 that these experiments will eventually throw considerable light upon 

 the causes which bring about the variations in the quantity of minute 

 vegetable life which take place in the sea itself. Since it is this 

 minute vegetable life which forms the fundamental food-supply of all 

 marine animals, an exact knowledge of the conditions under which it 

 can best flourish is of importance from both a theoretical and a 

 practical point of view. 



Mr. D. J. Matthews has been carrying out investigations on the 

 chemistry of sea-water. These investigations have Ijeen directed chietiy to 

 those points in which the Laboratory tank-water differs from the normal 

 sea- water of the district. Determinations of the hydrogen-ion concen- 

 tration by Sorensen's colorimetric method showed that the tank-water 

 was decidedly less alkaline than the outside water, the alkalinity meas- 

 ured by this process being the true alkalinity as opposed to the titration 

 alkalinity, which only measures the quantity of base combined with 

 acids volatile when boiled with a dilute mineral acid. Analysis has 

 shown that this deficient alkalinity is due not only to an excess of 

 carbonic acid, but also to a far greater excess of nitrates and phos- 

 phates. A quantity of carbonate of soda added gradually to the water 

 caused a considerable temporary improvement, and plutei were reared 

 nearly to metamorphosis under the circulation. The method has l)een 

 discontinued on the large scale on account of the continual rise in the 

 relative amount of sodium salts which it causes, but small-scale 

 experiments in which it is possible to measure the changes more 

 accurately and to keep a complete record of the results are being 



