GEPHYREA. 447 



solutions ; chromic solutions seem to have a tendency to make 

 the worms brittle. 



Staining is frequently difficult, and sometimes alcoholic 

 carmine, 170, is the only thing that will give fair results. 



BEAUN (see Journ. Roy. Mic. Soc., 1885, p. 897) recommends 

 that small unstained Nematodes be mounted in a mixture of 

 20 parts gelatin, 100 parts glycerin, 120 parts water, and 2 

 parts carbolic acid, which is melted at the moment of using. 

 Canada balsam, curiously enough, is sometimes found to make 

 Nematodes opaque. 



837. Acanthocephali. It is very difficult to kill Echino- 

 rhynci so as to have the animals duly extended and the tissues 

 well preserved. Neither corrosive sublimate nor strong osmic 

 acid will, as a rule, attain this end, even after preliminary 

 intoxication with tobacco smoke or chloroform, the animal 

 thus treated dying contracted. 



HAMANN, however (Jen. Zeit. f. Naturw., xxv, 1890, p. 113; 

 Zeit. f. wiss. MiJc. } viii, 2, 1891, p. 209), has succeeded with 

 sublimate, and also with alcohol containing a little platinum 

 chloride. 



SAEFFTIGEN (MorphoLJahrb., x, 1884, p. 120; Journ. Roy. Mic. 

 Soc. [N.S.], v, 1885, p. 147) obtained the best results by 

 killing gradually with 0*1 per cent, osmic acid; the animals 

 placed in this contract during the first hours, but stretch out 

 again and die fully extended. 



Another method of killing is treatment with O'l per cent, 

 chromic acid ; Echinorhynci live for days in it, but event- 

 ually die fully extended. 



KEISEE'S methods, see 41 and 61. 



838. Gephyrea. YOGT and YUNG (Anat. comp. prat., p. 373) 

 direct that Sipunculus nudus be kept for some days in per- 

 fectly clean basins of sea water, in order that the intestine of 

 the animals may be got free from sand, which would be an 

 obstacle to section cutting, and then anaesthetised with chloro- 

 form, under which treatment they die extended, and may be 

 fixed as desired. 



WARD (Bull. Mus. Comp. Zool., Cambridge, Harvard Coll., 

 xxi, 3, p. 144) found the best plan was to put the animals 

 into a shallow dish with sea water and pour 5 per cent, 

 alcohol in a thin film on to the surface of the water. After 



