SOME METHODS OF PREPAEING MARINE SPECIMENS. 217 



Picric acid, aqueous saturated solution . 75 parts 

 Formaldehyde (commercial 40 per cent.) . 25 „ 

 Acetic acid ...... 5 „ 



After fixation, wash out with alcohols of increasing strength, 

 starting with 25 per cent., stain, dehydrate, clear, and mount 

 in balsam. 



To those who wish to study the Hydrozoa and marine Polyzoa 

 with their tentacles fully expanded, it is a very real hardship 

 that, owing to the misuse of hydrochloride of cocaine, even the 

 1 per cent, solution necessary for narcotisation can only be 

 obtained through a doctor's order. A 1 per cent, solution of 

 cocaine in filtered sea-water is undoubtedly one of the best 

 narcotics for the Hydrozoa and Polyzoa, if perfectly extended 

 specimens are to be obtained. My method of using it is as 

 follows : The organism to be narcotised is placed in a small 

 petri dish containing just sufiicient sea-water to cover it and 

 permit of free movement. When the organism has expanded 

 fully, two drops of the 1 per cent, solution of cocaine from a 

 fine pipette are added, and the contents of the dish gently stirred 

 with a clean glass rod, care, of course, being taken not to touch 

 the organism in the process. Stirring is more important when 

 dealing with medusae than with colonies of hydroids or polyzoa. 

 After five minutes, another small dose is added, and this is repeated 

 at regular intervals, until there is no sign of contraction of the 

 body or tentacles on their being gently touched with a needle 

 or fine pipette. The small petri dish, or watch-glass, may then 

 be at once bodily lowered into a larger vessel filled with 4 per cent, 

 formaldehyde solution, which should be allowed to act for not 

 less than five minutes, stirring gently all the time if you are 

 treating medusae, so as to keep them ofi the bottom. The 

 organism is then removed with as little of the cocaine- 

 contaminated fluid as possible, and placed in a clean vessel 

 containing fresh 4 per cent, formaldehyde, and left for half an 

 hour, after which it is stored in 10 per cent, formaldehyde 

 solution. One important point to remember is that cocaine 

 has a softening action, and therefore the organism should never 

 be left longer in the solution than is absolutely necessary for 

 its complete narcotisation. Chloral hydrate will be found 

 even more objectionable in this respect. 



Menthol is a most useful narcotic, and one that deserves to 



