Echinoderma 



Crinoidea. — Antedon rosaces (Comatula) is put directly into 

 70 per cent alcohol, but A. phalangium, on account of its tendency 

 to break in pieces of itself, must be killed in that of 90 per cent 

 Shake the vessel violently to hasten death and prevent the animals 

 from breaking off their arms. When in doubt about the species use 

 90 per cent alcohol. 



The larval forms of the Pentacrinoids are narcotized with 

 chloral hydrate of 0.1 of 1 per cent — a process requiring two to 

 four hours. If they are then hardened in alcohol, they will re- 

 main with the arms perfectly distended. The more advanced stages 

 are best killed with saturated sublimate, where, however, they 

 should remain only a few moments to avoid injury to the membranes. 



Asteroidea. — To prepare the Stellarids with the ambulacral 

 feet in a state of distention, they are allowed to die in alcohol 

 of 20 to 30 per cent, being placed in the vessel ambulacra upper- 

 most. 



Luidia. — Lay the animal on its back in a shallow tray in 

 barely enough water to cover it. Then, when the ambulacral 

 tentacles, which are very long, are well distended, pour over it 

 the chrom-acetic mixture No. 2 and immediately transfer to 50 per 

 cent alcohol and after two hours remove to 70 per cent alcohol. 

 Small individuals may be killed with 55 per cent acetic acid, but 

 greater care must be used to transfer them to alcohol as soon as 

 dead. 



Brisinga easily breaks off its arms, to avoid which it 

 should be quickly immersed in absolute alcohol. 



Bipinnaria makes excellent preparations when killed with 

 the chrom-acetic mixture No. 1, and even better with the chrom- 

 osmic mixture, in which it should remain only a few minutes. Other 

 larval forms are treated with saturated sublimate solution. 



Some Ophiuroids are allowed to die in fresh water because 

 they thus remain distended and entire. Ophiothryx echinata is an 

 example. Certain small forms (Amphiura, Ophiactis) can be fixed 

 directly in weak 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. 



Echinoidea, — To prepare these with the ambulacral feet well 

 distended they are placed in just sea water enough to cover them 

 and an equal volume of chrom-acetic mixture No. 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. If 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 



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