380 PRESERVATION OF MARINE ORGANISMS 



70 per cent, alcohol. Formalin 5 per cent, may also be 

 used, but it does not give such good results, as it 

 attacks the carapace. 



Decapoda. Crabs, shrimps, prawns, etc., should be 

 killed in fresh water, and then put into 70 per cent, 

 alcohol. If put directly into alcohol, most of the 

 crabs are liable to throw off some of their legs. In the 

 case of crabs and lobsters larger than (say) half a 

 crown, it is advisable to slit up the membrane at the 

 back of the carapace with a sharp knife, so as to let the 

 alcohol get into the interior. 



For histological work on all Crustacea any of the 

 ordinary preserving fluids may be used, but they do 

 not easily penetrate the chitinous coat. Hot corrosive 

 sublimate probably gives the best result. Excellent 

 results may, however, be obtained with Flemming's, 

 Hermann's, and other fluids, if a specimen can be 

 obtained which has only just moulted and is in the 

 " soft " condition. The great secret of obtaining good 

 histological preparations of Crustacea is to use only 

 specimens in this condition, as not only is the preserva- 

 tion very much improved, but the making of sections 

 becomes easy, instead of wellnigh impossible. 



Polyzoa. For general purposes Polyzoa are best put 

 directly into 70 per cent, alcohol. This enables the 

 soft parts to be examined, or admits of the specimens 

 being easily dried for examination of the calcareous 

 skeleton. If it is wished to preserve the colour of a 

 colony, it should be washed with fresh water to re- 

 move the salt, and then dried in the air, without the 

 use of spirit. 



Bowerbankia-like forms and Ctenostomes in general 

 may be preserved in formalin. 



If it is desired to preserve material with the poly- 

 pites expanded, first anaesthetize with cocaine, and 



