BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [36] 



PleuropJiyllidia is narcotized witli alcoholized sea water and then 

 killed with concentrated acetic acid. 



Aplysia Umaeina and A. ptinctata are fixed in 1 per cent chromic acid, 

 where they are allowed to remain from fifteen to sixty minutes, accord- 

 ing to their size. A. depilans is narcotized in chloral hydrate solution 

 of 1 per cent (which may take twelve hours), killed with concentrated 

 acetic acid, transferred at once to chromic acid of 1 per cent, and after 

 half an hour put into 50 per cent alcohol, and so on. 



PleurobrancMa mecTceli is best treated with cocaine and then put into 

 chromic acid of 1 per cent, ^v^here the animals may remain about an 

 hour before they are washed and put into alcohol. 



Pleurohranchus meclieli and P. testudinarius may be killed in chromic 

 acid of 5 j)er cent. When scarcely dead the animals are transferred to 

 that of 1 per cent, where they may remain from fifteen to sixty minutes, 

 according to their size. The small specimens can be well prepared with 

 chloral hydrate, also, afterwards fixing them with chromic acid of 1 per 

 cent. 



Umbrella is slowly killed in alcoholized sea water, after which it is put 

 into weak alcohol. 



The Elysiidse and the JEolidiidse are permitted to expand in the least 

 practicable amount of sea water. They are then killed by rapidly pour- 

 ing over them a volume of concentrated acetic acid double or equal to 

 that of the sea water, and when scarcely dead they are transferred to 

 weak alcohol. 



Phyllirrhoe hucephalum is fixed in the chrom-osmic mixture for a few 

 minutes or in the chrom- acetic mixture No. 2. 



DoriSj CJiromodoris, etc. — The larger specimens of these animals may 

 be narcotized by adding 70 per cent alcohol, a little at a time, to the 

 water containing them, until touching the branchial appendages on the 

 back produces no contraction. They should then be killed with con- 

 centrated acetic acid or boiling saturated sublimate. If cocaine is used 

 for narcotizing the animals, they should be killed in concentrated acetic 

 acid, placed in chromic acid of 1 per cent for ten minutes and then 

 transferred to 50 per cent alcohol, and so on. The small specimens 

 need not be narcotized. 



Triopa, Idalia, and Polycera are treated like the Elysiidae. 



The large specimens of Tritonia are immersed until dead in fresh 

 water, to which a few drops of acetic acid have been added, when they 

 are hardened in chromic acid of one-half of 1 per cent. By this method 

 they remain well distended and the shape suffers no alteration. Small 

 Tritonias are treated with cocaine and then hardened and placed in 

 alcohol. 



Marionia is narcotized in alcoholized sea water and killed in acetic 

 acid. 



To prepare Tethys with the dorsal appendages in position, the animal 

 is allowed to expand in a large, low crystallizing dish in the least 

 amount of water possible necessary to cover it. It is killed by pouring 



