Methods of Preserving Marine Biological Specimens. 529 



Very nice preparations of compound Ascidians with contractile 

 zooids may be made by placing them for a few hours in clean sea- 

 water to expand, narcotizing with menthol, and then plunging into 

 glacial acetic acid. They should be left in the acid for three to ten 

 minutes, according to size, and then lifted out with wooden forceps 

 or the fingers, washed thoroughly in 50 p.c. alcohol, and then passed 

 through successive stronger grades in the usual way. On no 

 account should metal forceps be used, as they will cause a stain on 

 the place of contact with the organism. Salpa, Pyrosoma, and 

 other iree-swimming Tunicates may be killed and preserved in 

 10 p.c. formaldehyde. A small quantity of 1 p.c. solution of 

 chromic acid to the final formalin solution will help to further 

 harden the gelatinous test. 



Fish eggs and larvae should always be preserved in 5 p.c. 

 formaldehyde, as alcohol causes considerable shrinkage and contor- 

 tion ; and they are best mounted in cells filled with 5 p.c. 

 formaldehyde. 



Copepoda, Ostracoda, Amphipoda, Isopods, Cirripedes and 

 larval stage of Crustacea generally may be first treated with 5 p.c. 

 formaldehyde in sea-water, and then transferred to 70 p.c. alcohol. 

 Staining must be carried out with caution, as specimens are very 

 easily over-stained. Personally I prefer to use a weak alcoholic 

 picro-carmin stain, and to clear with turpineol, which does not 

 render the specimen too transparent, but beautifully translucent. 

 The specimen may be mounted direct from the turpineol, or first 

 washed in good purified benzol and mounted in balsam. 



Some examples of specimens prepared by the foregoing methods 

 are displayed under the series of microscopes. 



