JELLY-FISH 371 



others, and much depends upon the condition of the 

 specimens. 



The medusae may be left at the bottom of the vessel 

 for a few hours, and then they should be transferred 

 to a stronger solution of formalin about 5 per cent. 

 and finally stored away in formalin 10 per cent. 



To obtain medusae in a nice state of expansion, and 

 with tentacles stretched out, it is necessary to use an 

 anaesthetic. This gives a little extra trouble, but the 

 results are well worth the trouble when really nice 

 specimens are wanted. One of the best anaesthetics 

 is hydrochloride of cocaine, in either a i per cent, or 

 a 3 per cent, solution. 



Place the medusae in a small glass vessel with just 

 sufficient sea water for them to swim in. After they 

 have expanded, add a little cocaine (about 3 c.c. of 

 i per cent, for every ipo c.c. of sea water), and stir 

 gently with a glass rod to mix the cocaine with the 

 sea water. If the medusae at the end of about ten 

 to fifteen minutes have their tentacles expanded, and 

 do not contract when touched with a glass rod, no 

 more cocaine need be added ; but if still active, add 

 a Kttle more cocaine, and repeat the stirring process. 

 It is better to add about half the cocaine at first, and 

 gradually to increase the quantity, than to give the 

 whole dose at once. An overdose generally causes a 

 prolonged contraction. As soon as the medusae are 

 anaesthetized, stir them gently round and pour in the 

 formalin solution. Keep on stirring whilst the for- 

 malin is being added, and for a minute or longer after. 

 Specimens must not be left long in any solutions con- 

 taining cocaine, as it has a softening action upon the 

 jelly. A medusa anaesthetized with cocaine may also 

 be killed with picric acid, corrosive sublimate, or any 

 other good fixing solution. 



