FIXING AND PRESERVATIVE MEDIUMS 29 



colour the alcohol, or until, upon a drop of turpentine being 

 mixed with a drop of the treated alcohol, the microscope 

 reveals no particles of water as an admixture. 



It is said also (see Hamilton's Pathology, p. 54) that, 

 although methylated spirit is not absolute alcohol, it may be 

 made so " by the addition of a little dry carbonate of potash." 



" Sea-stars " such as Brisinga, which readily cast or break 

 their arms, are fixed by immersing them rapidly in absolute 

 alcohol (Lo Bianco, p. 458). 



1. — Al)solute Alcohol and Sea-water (Lo Bianco, p. 443) 



Alcohol (absolute) . . 5 parts 



Sea-water ., . . 100 „ 



The worm -like Hemichordate vertebrate,^ Balanoglossus, 

 has been narcotised in a well-extended position by this means. 



This is also used for narcotising and killing the Lamelli- 

 branch mollusca with their valves open. They should be left 

 in it from six to twelve or more hours, according to circum- 

 stances, and, when opened, a wedge of wood should be placed 

 between the valves. Certain other molluscs, such as " limpets," 

 " ear-shells," etc., are fixed extended in like manner, but none 

 should be transferred into the 70 per cent, alcohol until quite 

 dead, otherwise contraction is liable to take place. 



90 per cent. Alcohol. — Amphioxus, one of the Protochordata,^ 

 which, although a lowly vertebrate, is not, as Lo Bianco puts 

 it (p. 473), to be classed with the fishes, is easily fixed and 

 killed with the buccal cirrhus extended in — 



2. — Alcoholised Sea-water 



Alcohol (90 per cent.) . .10 parts 



Sea- water . . . 90 ,, 



^ See Amphioxus and the Ancestry of the Vertebrates, by Arthur Willey, B.Sc. 

 2 Ibid. 



