HOLOTHURIOIDEA. 451 



844. Hirudinea. For the methods of killing see those 

 given for Lumbricus in 841, also 14 to 19, and 811. 



WHITMAN (Meth.inmic. Anat., p. 27) recommends that they 

 be killed with sublimate. This reagent kills leeches with 

 such rapidity that they die in general without having time to 

 change the attitude in which they were found at the moment 

 when the liquid came into contact with them. 



Injection. WHITMAN (Amer. Natural., 1886, p. 318) states 

 that very perfect natural injections may often be obtained 

 from leeches that have been hardened in weak chromic acid 

 or other chromic liquid. He considers that these injections 

 are the best for the purpose of the study of the circulatory 

 system by means of sections. 



Of course Hirudinea (or any other Annelids) on which it is 

 desired to make artificial injections must be killed by some 

 procedure that leaves the tissues in a state that will allow the 

 injection to run freely. 



JAQUET (Mitth. Zool. Stat. Neapel, 1885, p. 298) advises 

 that leeches be put into water with a very small quantity of 

 chloroform ; they soon fall to the bottom of the vessel and 

 remain motionless. They should be allowed to remain a day 

 or two in the water before injecting them. 



Echinodermata. 



845. Holothurioidea. These animals are difficult to fix on 

 account of their contracting with such violence under the in- 

 fluence of irritating reagents as to expel their viscera through 

 the oral or cloacal aperture. It has been recommended that 

 they be seized by the middle of the body and firmly squeezed 

 in the hand, and so plunged in a fixing liquid (acetic acid, for 

 instance), or that they be ansesthetised (in the case of Synapta 

 and Gucumaria) by adding ether to the water in which they 

 are contained. So far as my experience goes, I am bound to 

 say that I know no better way of killing them than that of 

 simply putting them into fresh water, in which they generally 

 die without contraction, and with their tentacles extended. 

 Of course the histological preservation of the parts is 

 detestable. 



S. Lo BIANCO puts Holothurids into pure sea water until 

 they have expanded their tentacles, then seizes them with 



