PKOGRESS IN BIOLOGICAL INQUIEIES, 1921. 



31 



winter the number fell to 1,500 per c. c. In the spring and early summer of 

 1920 the number rose steadily to a maximum average of about 30,000 per c. c. 

 from the latter part of June to the end of August. During the autumn and 

 early winter the number gradually declined to an average of 2,000 bacteria per 

 c. c. of water. 



Many of the bacteria represent chromogenic forms, and various colors are 

 found in the plate cultures. There seem to be some denitrifying individuals 

 present, but conclusive evidence of the presence of lime-precipitating forms 

 has not been obtained yet. The average size of these bacteria has been obtained 

 so that it will be possible to estimate their live weight and dry weight as well 

 as the organic matter in them. 



3. Several reports are now in press in the Transactions of the Wisconsin 

 Academy which deal with investigations in which the Bureau of Fisheries has 

 cooperated. The following may be listed here : "A survey of the larger aquatic 

 plants of Lake Mendota," by R. H. Denniston ; " A quantitative study of the 

 larger aquatic plants of Lake Mendota," by H. W. Rickett; "A quantitative 

 study of the bottom fauna in the deeper water of Lake Mendota," by C. Juday. 



Some chemical analyses of the larger aquatic plants from Lake Mendota 

 have also been made, but this has been done independently by the Wisconsin 

 Survey. 



4. Various analyses have shown that the quantity of organic nitrogen in the 

 lake water itself amounts to five or six times as much as that in the total 

 plankton, and Dr. Schuette has been trying to work out a method for the 

 determination of this dissolved organic nitrogen which will give results that 

 are more satisfactory than the present methods of nitrogen determination. 

 The quantities are so small that the methods now used by chemists do not 

 always give consistent results. So far no other method has been found which 

 will give better results than the standard methods. 



AGAR-AGAR AND OTHER GELATINS FROM SEAWEED. 



It is obviously unfortunate that the United States should be de- 

 pendent upon other countries for its supply of a vital necessity. 

 Agar- agar is the commercial name applied to a gelatinous product, 

 which has been imported from Japan, China, and other places, the 

 importations in 1919 amounting to nearly half a million dollars. 

 The importance of the material is not, however, measured by its 

 strictly commercial value. While it is used in making food and 

 confections, agar-agar is primarily important because it is a necessary 

 medium for bacteriological work, and is therefore essential to medi- 

 cal laboratories and hospitals. It is a requisite for certain industries, 

 for the maintenance of health, and for national security. 



Marine algse or seaweed have long been used in this country for 

 the preparation of gelatins for particular purposes, but only the 

 recent investigations, conducted for the Bureau by Dr. Irving A. 

 Field,^ have revealed the fact that we have possible sources of supply 

 for the most valuable gelatin of all in certain species of seaweed on 

 the west coast. In the report for the preceding year reference was 

 made to Dr. Field's preparation of a gelatin suitable for use in pre- 

 serving fish, and to experiments in producing a substitute for agar 

 from Atlantic coast seaweed. These experiments were not successful, 

 but it w^as later ascertained that at least one species of the west coast 

 yields agar of the best quality. Agar prepared by Dr. Field and 

 tested at the Army Medical School in Washington was pronounced 

 equal or superior to the imported agar. Another species yielded a 

 product apparently of like quality. The investigation should be 

 followed by a field survey for the purpose of definitely locating the 



^ Field, I. A. : Sources, Preparation, and Properties of Some Algal Gelatines. Bureau 

 of Fisheries, BcoLomic Circular No. 51, issued Oct. 10. 1921, 7 p. Washington. 



