368 E. J. ALLEN AND E. W. NELSON. 



Skeletonetna costatum (Grev.). 

 vStreptotheca thamensis ShruVjs, 

 Thalassiosira decipiens Grun.^ 

 • It is hardly necessary to add that in dealing with these 

 cultures similar precautions to those used in bacteriological 

 work must be taken, all vessels and instruments being care- 

 fully sterilised before they are brought into contact with the 

 piepared sea-water. The cultures are best made in small, 

 wide-mouthed flasks, which may be plugged with cotton-wool, 

 or simply covered with watch-glasses. The flasks should be 

 kept at as uniform atemperature as possible (from 12*^-17° C.) 

 and should be exposed to strong daylight, direct sunlight 

 being avoided. A fiask should not be more than half filled 

 with culture fluid, so that the surface exposed to the air may 

 be large in proportion to the volume of fluid. 



Other Methods. — The addition of the solutions devised 

 by Miquel to sea-water has in all cases given us good cultures 

 of diatoms, and the method is certain in its action. We have, 

 however, made numerous experiments by treating sea-water 

 in other ways, with a view to finding out what are the best 

 conditions under which plankton diatoms will grow, and of 

 arriving at some explanation of the action of the different 

 salts contained in j\Iiquel's solutions. 



2. Houghton Gill's Method.— H. Houghton Gill (5), 

 a contemporary of Miquel, made use of a culture medium not 

 essentially different from that employed by the latter. Unfor- 

 tunately he died before publishing his work, but an account 

 of his principal results is given by Van Heurck. In his final 

 ii^ethod Houghton Gill made use of four distinct solutions, as 

 follows : 



Solution 1 . 



Crystallised sodium phosphate 



Calcium chloride . . 



Syrup of iron chloride 



Strong hydrochloric acid 



Water . . ... 

 1 See p. 412. 



