584 SUMMARY OF CURRENT RESEARCHES RELATING TO 



will produce a result) be added to the artificial medium and the whole 

 sterilized, excellent cultures are obtained which are often better than 

 any which have been got when natural sea-water forms the foundation 

 of the culture medium. 



The result appears to be due to some specific substance present in 

 minute quantity in the natural sea-water, which is essential to the 

 vigorous growth of the diatoms. The nature of this substance it has 

 not been possible to determine, but some evidence seems to suggest that 

 it is a somewhat stable organic compound. Provided that 1 p.c. of natural 

 sea- water is added, the various constituents of the artificial sea-water 

 forming the basis of the culture medium can be varied in amount within 

 wide limits. The salinity of the medium can also be considerably 

 altered without serious detriment to the cultures. 



The experiments recorded are of interest as furnishing another 

 instance of the importance in food substances of minute traces of 

 particular chemical compounds. They may also eventually throw light 

 upon the nature of the conditions in the sea, which are specially favour- 

 able to the production of plant life, and therefore also of the animal life 

 which that plant life sustains. In connexion with the foregoing, allusion 

 is made to W. B. Bottomley's paper on Accessory Factors in Plant 

 Growth and Nutrition.* The experiments of Gowland Hopkins on the 

 feeding of rats also bear on the same point. 



Growth of certain Fresh-water and Soil Protista.f — H. G. 

 Thornton and G. Smith record most interesting experiments with the 

 object of indicating certain lines upon which it may be possible to attack 

 the problem of cyclical development in ponds and lakes. The general 

 results they arrive at are that, as compared with Euglena, soil flagellates 

 are able to live in cultures to which organic compounds of very varying 

 nature have been added. This comparative impartiality is the result of 

 the holozoic mode of nutrition, the development of the flagellates being 

 absolutely dependent on the bacterial growth. The presence of the Miquel 

 salts in the solution is necessary for the growth of the soil flagellates and 

 for the proper development of the bacteria upon which they feed. The 

 flagellates can feed upon a variety of different types of bacteria. 



Method of Making Cultivation Media without Prepared 

 Peptones. J — S. R. Douglas describes a method of media making which 

 gives constantly an efficient medium, and has proved more simple and 

 easier than Haffkine's method. Fresh bullocks' hearts having been 

 obtained, the fat and large vessels are removed. The meat is then 

 finely minced, and to the mince thus obtained from an average-size 

 heart four litres of water are added. This mixture, after being 

 thoroughly stirred and rendered faintly alkaline to litmus, is heated to 

 between 70° and 80° C. After cooling to 45" C. 1 p.c. of trypsin solution 

 (40 c.cm. to the 4 litres) is added, the preparation of trypsin used being 

 Allen and Hanbury's liquor trypsin co. This, in view of the fact that 



* Proc, Roy. Soc, lxxxviii. (1914) p. 237. 



t Proc. Roy. Soc, lxxxviii. Ser. B (1914) pp. 151-65 (1 pi.) 



t Lancet, 1914, ii. pp. 891-2. 



