376 PRESERVATION OF MARINE ORGANISMS 



the preserving fluid to enter, and the specimen be 

 preserved in 2 per cent, chromic acid, washed in run- 

 ning water, and transferred to 70 per cent, alcohol ; 

 or the specimen may be placed at once in formalin- 

 spirit, or 5 per cent, formalin, without the use of 

 chromic acid. 



Antedon. Specimens thrown flat into a shallow 

 dish of strong spirit give good results. There should 

 be just enough spirit to cover the specimens. 



Echinoids. Echinus and similar forms may be pre- 

 served with the tube feet expanded by transferring a 

 healthy specimen suddenly to strong acetic acid or to 

 warm 70 per cent, alcohol. If only the internal parts 

 are required, a hole should be made in the shell, and 

 the specimen put at once into 70 per cent, spirit, or 

 into formalin-spirit. 



Holothurians. Specimens merely killed in spirit, and 

 with spirit also injected by the anus, are sufficient for 

 the purposes of the ordinary collector. 



Formalin and all acids should be avoided, as it is 

 important not to injure the calcareous plates in the 

 skin. 



But if nicely expanded specimens are desired, they 

 should be anaesthetized in the ordinary way with 

 menthol (about twelve hours). They will then gener- 

 ally remain expanded. As soon as they cease to 

 react when the tentacles are touched, they may be 

 transferred to 70 per cent, spirit, and at the same time 

 injected with 90 per cent, spirit through the anus. 



Polychaeta. To preserve these worms the following 

 has proved to be the most useful general method : The 

 worms are first placed in a vessel of clean sea water, 

 and 70 per cent, alcohol is added drop by drop, and 

 mixed by gentle stirring with the sea water. The 

 operation is repeated every few minutes, the dose of 



