BRITISH ZOOPHYTES. 339 



up to 60 per cent.* The strength of spirit may be 

 ultimately iucreased to 90 per cent. Another excellent 

 method is to use Kleinenberg's fluid prepared as 

 follows : — 



Water, 100 volumes. Sulphui-ic acid (concentrated), 

 2 vols. Picric acid (as much as will dissolve) . Filter 

 and dilute with three times its bulk of water. 



This fluid should be used in the same way as alcohol, 

 and the objects left in for three or four hours, and 

 afterwards passed to 70 per cent, and ultimately 90 

 per cent, alcohol. This method is largely used at the 

 Naples Zoological station. f 



A one per cent, solution of osmic acid is sometimes 

 recommended as a medium for rapidly killing zoophytes, 

 but it has the quality not only of killing them, but of 

 blackening them at the same time. The black stain, 

 however, may be removed by bleaching in a weak 

 aqueous solution of ferrocyanide of potassium, the 

 specimen being afterwards thoroughly washed. 



The majority of zoophytes cannot be mounted as 

 transparent objects, and must be mounted so as to be 

 viewed by reflected light. To accomplish this, the 

 specimen should be well cleansed, cai-e being of course 

 taken not to damage the spines or protuberances, if 

 any, and mounted in a cell having a neat black back- 

 ground, or for some species, as S.fusca, a white back- 

 ground. The cell should be made in such a way that 



* See A. D. Michael, Journ. Queckett Club, i. (1883), p. 241, 

 and H. C. Chadwick, " Microscopical News," vol. i. (1883), and 

 " Science Monthly," Januaiy, 1884, 92. I have seen a number of 

 beautifully mounted slides by the latter writer. 



t See article by Mr. C. 0. Whitman in the Postal Micr. See. 

 Journal, vol. ii. 99. 



Z 2 



