PROGRESS IN BIOLOGICAL INQUIRIES, 1922. 25 



considerably increased, although complete control was never at- 

 tained. In two other experiments when the fish were killed in 

 ponds containing barriers mosquito production increased at least 

 eightfold in one instance and ninefold in the other, as indicated by 

 a comparison of counts made of immature mosquitoes taken in 

 weekly dippings in the Ashless ponds and similar dippings made in 

 the " control " ponds. It appeared then that even if effective bar- 

 riers are present a great reduction in mosquito production is brought 

 about by the fish. 



The most practical way of manipulating the various plant barriers 

 in order to render them useless as protectors of mosquito larvae 

 requires much more study, but it was found that half measures in 

 the removal of silver-leaf grass were more detrimental than none 

 at all. The grass affords more protection to mosquito larvae when 

 it is merely thinned than when it is more rank. Again, after cut- 

 ting, the plant becomes effective in protecting mosquitoes just at 

 the moment when its growing stem attains the surface of the water. 

 The experiments showed that, if the removal of silver-leaf grass is 

 undertaken, the work must be thoroughly done and repeated as soon 

 as the plant again appears at the surface. 



REDDENING OF SALT FISH. 



A iew years ago the bureau conducted investigations of the causes 

 and possible remedies for the red infection of salt fish, a condition 

 that causes substantial losses to packers of salt fish on the New Eng- 

 land coast. The investigations threw much light upon the causes 

 but developed no practicable means of prevention. 



With the beginning of the fiscal year 1922, the investigations were 

 resumed with the employment of Alfred A. Ellsworth, of the Mass- 

 achusetts Institute of Technology, as investigator. During the year 

 the work of the investigator was devoted largely to developing the 

 special bacteriological technique and the studies of various single 

 factors of growth under laboratory conditions. Progress has been 

 made in acquiring information regarding the causative organisms, 

 but a report of results must be deferred until the investigation is 

 further advanced. 



THE BIOLOGICAL LABORATORIES. 



Because of the limitation of funds and the corresponding inade- 

 quacy of personnel, both permanent and temporary, the biological 

 laboratory at Woods Hole, Mass., was not operated by the bureau 

 during the summer of 1921. That the station might not, however, 

 fail to serve a useful purpose during that season it was deemed 

 proper to extend the use of the laboratory rooms to the Marine 

 Biological Laboratory of Woods Hole upon the understanding 

 that no charge would be made by that institution for the use of 

 Government facilities and that no expense to the Government 

 would be involved. In the early part of the summer of 1922 the 

 laboratory was reopened. Dr. R. E. Coker, assistant in charge of 

 scientific inquiry, acting as director for the greater part of the 

 season. From the station, as laboratory headquarters, there is be- 

 ing conducted by Dr. P. S. Galtsoff the biological survey of Long 



