METHODS OE COLLECTING AND 

 PRESERVING VARIOUS INVERTEBRATE 



ANIMALS. 



I. GENERAL. 



Alcohol is indispensable as preservative fluid ; but certain pre- 

 cautions are necessary in its use. Except in a very few cases it is 

 unnecessary to use it in its full strength, 70 per cent, being quite 

 sufficient for preservation, and producing much less contraction and 

 fragility in delicate organisms. Strong alcohol should be reduced 

 with distilled water to the desired strength, as ordinary spring- water 

 frequently contains a sufficient amount of carbonate of lime and 

 other substances in solution to give a cloudy precipitate, which may 

 effectually destroy the appearance of a specimen. 



Furthermore, it is desirable that animals should first be placed in 

 weak alcohol (from 35 to 50 per cent.) for from two to six hours. 

 Some of the weak spirit should then be drawn off and stronger 

 added until the desired strength is obtained. With delic:ite gelatinous 

 structures the increase in the strength of the alcohol should be as 

 gradual as possible. The process of placing specimens successively 

 into alcohols gradually increasing in strengtli is known as '• grading." 



Formalin or formol has bean much used of late years on account 

 of its portability and cheapness. Commercial formalin is a 40 per 

 cent, solution of formaldehyde in water. The strength of formnlin 

 now most recommended for general purposes is a 10 per cent, solu- 

 tion {i.e. 4 per cent, formaldehyde), made by diluting one part of 

 commercial formalin with nine parts of water. The mixture, when 

 used for preserving, should be poured away after 24 hours, and fresh 

 solution added ; and, further, the bottles should be securely sealed. 



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