to alcohol as soon as dead. If the individuals are very small, 

 the pressure on the neck should be made with forceps instead of 

 the fingers. 



Cucumaria plancii is treated like the large Holothurians, 

 except that the injection of alcohol is made through the mouth, 

 taking care to keep the tentacles distended, and it is not 

 necessary to close the opening with a cork. The other species 

 of Cucumaria are killed in the same manner. It is not necessary 

 to inject the small specimens. 



The large Synapta, in the preparation of which much diffi- 

 culty has been experienced on account of its tendency to break 

 to pieces, is killed by immersion in a tube containing sea water 

 and ether in equal parts. In this mixture the animals usually 

 die completely distended. When dead and well distended, they 

 are washed in fresh water and put into weak alcohol. The trans- 

 fer to 70 per cent alcohol should be very gradual, to avoid con- 

 traction. Chloroform may be used instead of ether. The harden- 

 ing may also be done by putting 2 or 3 c.c. of 1 per cent chromic 

 acid into the water in which they have been washed. After a few 

 seconds remove to weak alcohol. 



-p- The rare Molpadia musculus and the little Chirodota venusta 



have been also prepared by this method. Auricular ia is best kill- 

 ed in the mixture of sulphate of copper and sublimate or in sub- 

 limate alone. 



Enter opneusta 



Balanoglossus is killed with the Kleinenberg solution or 

 in chromic acid of one-half of 1 per cent, but the former is much 

 better. When narcotized in alcoholized sea water the animals re- 

 main well distended and straight. Tornaria is killed with the 

 sulphate of copper and sublimate mixture. It is well preserved 

 also with saturated sublimate or with the chrom-osmic mixture. 



Vermes 



The Cestodes are fixed with cold saturated sublimate, the 

 Trematodes with the same solution hot. If it is desired to have 

 flat preparations to mount for the microscope, the animals should 

 be placed between two plates of glass, which are brought together 

 by gradual pressure, and then placed in a crystallizing dish under 

 moderate weights. When the animals are flattened enough and there 

 is as little water as is practicable in the dish, pour over them 

 boiling saturated sublimate and leave them therein until they 

 show no signs of contraction. Then, the plates of glass being , 

 removed, the worms are allowed to harden thoroughly in cold satu- 

 rated sublimate, since the boiling sublimate fixes only the margins 



- 36 - 



