CRUSTACEANS — INVERTEBRATES 63 



Most invertebrates are best preserved in alcohol. For per- 

 manent preservation a 70 percent solution is used. Certain animals 

 become too rigid or brittle and others excessively contracted 

 when killed in solutions that are too strong. Therefore all 

 animals should be killed in 30 or 40 percent alcohol. Marine 

 crustaceans, shrimps and crabs, that spend their lives in the sea, 

 may be killed by placing them in containers of fresh water. 

 Those that live on land or in fresh water must be killed in the 

 weak alcohol. As far as practicable, animals should be killed in 

 individual containers. This is especially important with larger 

 specimens, such as crabs, as if placed together they often fight 

 and tear each other. Tin cans are useful as killing containers. 



Immediately after death, time and materials permitting, the 

 killed specimens should be put into a 60 per cent solution of 

 alcohol overnight before being transferred to the final 70 percent 

 solution for permanent preservation. If there is no time for this, 

 they may be placed directly in a 70 percent solution from the 

 weak killing solution. In lieu of other preservatives, strong 

 spirits, such as whisky or rum, will usually preserve invertebrates 

 until they can be given further attention. Since the alcohol is 

 diluted by the extracted body fluids of the animals, it is advisable 

 either to change it or to bring it up to 70 percent strength by 

 adding undiluted alcohol after a day or two. Use fresh water to 

 dilute alcohol. 



Formalin makes a good pickling solution for all types of 

 animals if alcohol is not available, and is the best preservative 

 for jellyfish. The commercial article, formaldehyde, is usually 

 labeled as being a 37 percent solution of formic acid in water. 

 This is mixed in proportion of 1 part of formalin to 20 parts of 



