124 THE PRESERVATION OF MARINE ANIMALS 



former is killed in the chrom-osmic mixture, in which it is to remain 

 fifteen to thirty minutes, before being transferred to alcohol. Bero'e 

 is simply placed directly in alcohol, 70 per cent., but before 

 immersion in this a short piece of wide glass tube is placed in the 

 gastric cavity, a bubble of air being left in the tube so as to cause 

 the specimen to float in the alcohol. The tube keeps the specimen 

 in its natural cylindrical form, but great care must be exercised in 

 the manipulation. 



Echinodermata. — In order to prepare star-fishes with the 

 ambulacral feet distended, they should be allowed to die in alcohol 

 of 20 to 30 per cent., with their ambulacral surface uppermost. 

 Ophmroidea should be killed in fresh water and placed in alcohol 

 when dead. 



Sea-urchins are to be placed in a small quantity of sea water, and 

 when their tube-feet are extended a mixture of acetic acid 100 parts, 

 chromic acid (i per cent.) ten parts, is poured suddenly over them. 

 They must be removed into alcohol immediately afterwards, so that 

 the acid may not have time to act on the shell. When placed in the 

 alcohol two small holes should be made at opposite points of the 

 shell to allow the alcohol to enter the interior, and care must be 

 taken in transferring the specimens to stronger alcohol, that the 

 interior is emptied and then refilled with the latter. To prepare sea- 

 urchins dry, holes should be made in them in the same manner, and 

 then they should be placed in 70 per cent, alcohol for a day or two, 

 after which they can be taken out and left to dry. 



Holothurians are extremely difficult to fix in their natural 

 extended condition. The method to be followed with large speci- 

 mens is to seize them when expanded with finger and thumb behind 

 the base of the tentacles and plunge the anterior part of the body 

 into pure acetic acid, while another person injects alcohol of 90 per 

 cent, into the specimen /^r aiium with a syringe. As soon as it is 

 dead, the specimen is placed in 70 per cent, alcohol, a cork being 

 placed in the anal orifice to prevent the escape of the injected liquid. 

 Smaller specimens are treated in the same way, omitting the injection, 

 and using forceps instead of the fingers. 



Planarians are to be killed by pouring over them boiling corro- 

 sive sublimate in saturated solution, turning them out immediately 

 they are dead into cold fresh water, and after washing them placing 

 them in alcohol. 



Nemerteans should be narcotized in a solution of chloral 



