BULLETIN 89, UNITED STATES NATIONAL MUSEUM. [28] 



alcohol, shaking the vessel violently to hasten death. Ophiomyxa 

 pentagona, which has a soft body, is hardened in chromic acid of one-half 

 per cent. Ophiopsila annulosa breaks in pieces of itself in fresh water, 

 and is therefore killed in absolute alcohol. 



Ecliinoidea. — To i^repare these with the anibulacral feet well distended 

 they are placed in just sea water enough to cover them and an equal 

 volume of chroni-acetic mixture ISTo. 2 is poured into the jar. They 

 must be transferred at once to alcohol, so as not to give time to the acid 

 to corrode the calcium carbonate of the animal. I f desirable to preserve 

 the soft parts of the animal for anatomical purposes, or even for form 

 only, two small holes must be made in the shell opposite each other to 

 discharge all the fluid contained therein. After immersion in alcohol' 

 one must see that the liquid tills the internal cavity, and, on changing 

 the animal to stronger alcohol, that the liquid contained within the 

 shell is changed also. 



If dry specimens of echini are wished, discharge the water within the 

 shells and let the animals lie in ordinary 70 per cent alcohol for one or 

 two days before placing them in the wind and sun to dry. Starfish also 

 make better dried specimens if they are killed in 70 per cent alcohol 

 and allowed to remain there two or three days before they are dried. 



Holothurioidea. — Holothurians require more care than other echino- 

 derms, because they have soft and very contractile bodies and all are 

 furnished with tentacles which contract or retire within the body on 

 contact with a reagent. Some species, furthermore, soon after they are 

 immersed in the fixing fluid expel their viscera and become valueless 

 as specimens — a thing which may happen in the sea water also, if that 

 is changed too suddenly. All these inconveniences are avoided by 

 treating the animals by the methods here described. 



First of all, as with other animals which must become expanded, 

 they are placed in clear sea water. Those species whit-h are killed in 

 acids should be allowed to remain in them only just long enough to 

 cause death, so that the calcareous cutaneous spicules be not injured. 

 Large specimens of Holothuria and Stichopits as soon as the tentacles 

 are fully distended should be seized with two fingers, or with a pair of 

 forceps, a little below the tentacles, lifted from the sea water, and be 

 immersed as to the anterior portion only in a rather deep vessel con- 

 taining concentrated acetic acid. At tlie same time another person 

 should inject some 90 per cent alcohol into the animal through the anal 

 aperture with a syringe, taking care not to exert too great pressure, 

 lest the body be distended too much. Before the Holothurian is quite 

 dead it is to be immersed in 70 per cent alcohol, closing the anal orifice 

 with a small cork to prevent the escape of the liquid and the conse- 

 quent flattening of the body. The injection should be repeated at each 

 successive renewal of the alcohol. 



With certain species, as, for example, Holothuria poli, the operations 

 must be performed with much caution, because the skin is easily 

 injured. 



