PROGRESS IN BIOLOGICAL INQUIRIES. 27 



as temporary investigator. The chief purpose is to determine the 

 normal biolofjical and physical conditions throufrhout the year. This 

 done, there would thou be normal data at hand from which to deter- 

 mine the abnormal conditions which bring about such serious mor- 

 talities of lish or oysters as have occurred in previous years. The 

 survey should reveal all that is possible regarding the movements 

 of layers of water of different densities, different temperatures, and 

 different fish-food values, and should indirectly throw light upon the 

 migrations of fish and crabs into or about the Bay. Special attention 

 wdll be given to the "deep holes" and to the alleged barren bottoms 

 at the mouths of rivers, and, throuf^h the collection of bottom de- 

 posits and the collaboration of the United States Geological Survey, 

 information of value to geologists will be secured. In general the 

 purpose is to gather as much as possible of the data which are essen- 

 tial for the conservation and development of the fisheries of this 

 important body of water. 



BIOLOGICAL AND PHYSICAL STUDIES OF INLAND LAtlES. 



The Bureau has continued to cooperate with the Wisconsin Bio- 

 logical and Natural History Survey in the studies of the fundamental 

 conditions of inland lakes. The principal burden of these investi- 

 gations is borne by the State, but it is not out of place to present here 

 a brief statement of the status of the work, based upon a progress 

 report submitted by President E. A. Birge and Mr. Chancey Juday. 

 Bulletins on the plankton algae, on gravimetric and chemical analy- 

 ses of the plankton of the lakes in the vicinity of Madison, and on the 

 bottom fauna in deeper water of Lake Mendota are now substantially 

 or entirely completed. These reports comprise descriptions of many 

 of the plankton elements and other units of fish-food supply, data 

 regarding chemical composition (the basis of food value), and meas- 

 ures and computations of the quantities of the crops of organisms 

 which maintain the productiveness of lakes in fish. Studies of the 

 bacteria of Lake Mendota are in progress. 



MISCELLANEOUS STUDIES. 

 REDDENING OF SALT FISH. 



The salt-fish industry of the United States suffers a large annual 

 loss as a result of the salt fish developing a red coloration when stored 

 under moist conditions. Investigations conducted for the Bureau by 

 Dr. W. W. BrowMie indicate that the development of the red colora- 

 tion is due to the growth of two microorganisms, wdiose probable 

 origin is the sea salt in which the fish are cured. This coloration 

 may vary fi-om a pale pink to a deep crimson. The pale pink colora- 

 tion is produced as a result of the grow^th of a spirochete and the 

 deep red by a bacillus form: these two organisms may, however, 

 grow in such close harmony that the pigmentation may vary from 

 ;i pale pink to red. It was formerly thought that the varied pig- 

 mentation was due to varied dilutions of the red pigment. The sepa- 

 ration of the two organisms is very difficult owing to this close union. 



The optimum concentration of salt for the growth of these micro- 

 organisms seems to be saturation. Thoy grow well on heavily salted 



