1896.] MICROSCOPICAL JOURNAL. 95 



must be stated now, after examination of these figures, 

 that mechanical filtration under these conditions can be 

 firmly indorsed. 



Cocaine in the Study of Pond-Life. 



H. N. CONSER. 

 Member of American Microscopical Society. 



SUNBUEY, PA. 



Hydrochlorate of cocaine as a narcotic for forms of 

 aquatic life has a special value in the study of bryozoans 

 and the encased rotifers. Quick-killing methods cannot 

 be used where the contractile organs are so well protected 

 as in these forms, neither can the narcotics that kill, for 

 they often allow disorganization of cilia and tentacles be- 

 fore other parts of the organism are suflBciently benumbed. 



The method I have found most satisfactory and certain 

 with the fresh water Bryozoa is as follows : Several 

 colonies are placed in a solid watch glass with 5 cc. of 

 water, and as soon as the animals have expanded, one or 

 two centigrams of cocaine is dropped on the edge of the 

 water^t two or three distant points. In fifteen minutes 

 the narcotic inflence is suflficient, as can be tested by 

 touching the tentacles with a needle. One per cent 

 chromic acid is now poured in to fill the watch glass and 

 left to act for half an hour or more when it is nearly all 

 withdrawn and water substituted. This process is re- 

 peated in half an hour and alcohol to form aTDOut twenty- 

 five per cent added to the water, the strength of alcohol 

 is increased by the addition of ninety-five per cent until 

 eighty per cent is reached. By this means the chromic 

 acid is washed out and the hardening accomplished so 

 gradually that no distortions occur. For staining, borax- 

 carmine or alcoholic-cochineal is used. The clearing 

 must be gradual and is best accomplished by adding oil 

 of lavender to the ninety-five per cent alcohol in which 



