374 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Artificial .Culture of Marine Plankton Organisms.* — E. J. Allan 

 and E. W. Nelson give an account of an extended research into methods 

 of cultivating plankton diatoms in sea-water media. In their paper 

 they call any diatom culture which can be carried on practically in- 

 definitely by inoculating fresh supplies of prepared water, a " persistent " 

 culture. Strictly " pure " cultures have not been obtained, but most of 

 the " persistent " cultures contain only one species of diatom, and are 

 free from all organisms larger than small flagellates. 



As culture media, the authors used' sea-water (" outside " water or 

 " tank " water), sterilised and unsterilised, prepared either by the 

 addition of Miquel's saline solutions or the authors' modifications of these 

 solutions, or in other cases by treatment with animal charcoal or peroxide 

 of hydrogen. It was found unnecessary to add the organic infusion 

 recommended by Miquel. The best medium was found to be sterilised 

 " outside " water (i.e. water from the English Channel) treated with 

 Miquel's solutions, and the next best was sterilised tank water treated 

 with animal charcoal. 



In order to discover the conditions which underlie the successful 

 cultivation of diatoms, they exposed a number of cultures to varying 

 conditions of salinity and alkalinity as well as to varying degrees of 

 light and temperature. It seems necessary to raise the concentration of 

 nitrates, or possibly of phosphates, above that found in ordinary sea- 

 water. The influence of hydrogen peroxide or animal charcoal appears 

 partly nutritive, partly protective, effecting the removal of toxic sub- 

 stances. Light is the most important physical factor, the rate of growth 

 in a suitable medium depending directly upon its intensity. 



A number of flasks were inoculated with mixed cultures by taking 

 plankton fresh from the sea. In general, the true plankton diatoms are 

 the first to develop in considerable numbers. After two or three weeks, 

 infusoria, alga?, and the bottom diatoms, gain the upper hand, and the 

 true plankton forms die out. 



The remainder of the paper is devoted to the study of the life-history 

 of certain species of diatoms, and to the methods of rearing marine 

 larvae in sterile sea-water with a pure culture of a suitable food. 



Simple Anaerobic Methods.f — A. Tedeschi gives an account of his 

 application of Marino's methods. For the isolation of anaerobes he uses 

 a culture medium pressed between two sterile-glass surfaces. The medium 

 is inoculated and kept at a temperature of 42° 0. for half an hour. It is 

 then poured into the inverted cover of a Petri dish, and then the Petri 

 dish itself is placed with its outer surface upon the surface of the 

 nutrient medium. If the surface of the glass is even, access of air is thus 

 excluded. 



The author is also able to cultivate anaerobes in deep culture in 

 ordinary agar. The medium is melted and cooled to 42° C, at which 

 temperature it remains liquid. Sterile glass beads are dipped in broth 

 — to remove adherent air — inoculated with the culture material, and 

 dropped into the agar. They fall to the bottom of the tube, carrying the 

 inoculum with them. 



* Journ. Marine Biol. Assoc, Plymouth, viii. (1910) pp. 421-74. 

 t Centralbl. Bakt., lte Abt. Orig.', liv. (1910) pp. 105-8. 



