TREMATODES. 443 



on account of the brittleness of the tissues, caused by the 

 preliminary treatment with turpentine or oil of cloves. I 

 fancy that this difficulty would be easily overcome by clearing 

 with cedar oil instead of clove oil, as I have constantly recom- 

 mended for the special purpose of avoiding brittleness in 

 tissues. 



829. Macrotoma plumbea (SOMMER, Inaug. Diss., 1884, p. 4; 

 Zeit. f. wiss. Mik., 1885, p. 234). Fix with boiling water ac- 

 cording to the method of Rossler, last section, and harden for 

 several hours in picro-sulphuric acid diluted with 5 volumes 

 of water. Penetrate with chloroform and imbed in paraffin. 



830. Aphidae (see ante, 621). 



831. Other Methods for Arthropoda. For Embryological 

 methods see Chap. XXY, 616627. 



For Sperm atological methods see Chap. XXYI, 645. 



Vermes. 



832. Cestodes. This group must of course be chiefly studied 

 by the usual section methods. It is only necessary here to- 

 remind the reader that, as pointed out by YOGT and YUNG 

 (Trait. d'Anat. comp. prat., p. 204), the observation of the 

 living animal may be of service, especially in the study of the 

 excretory system. And, as shown by PINTNBE, taeniao may be 

 preserved alive for several days in common water to which a 

 little white of egg has been added. 



LONNBERG (Centralb. f. Bakteriol. u. Parasitenk., xi, 1892,. 

 p. 89; Journ. Roy. Mic. 8oc., 1892, p. 281) has kept Tri&no- 

 phorus nodulosus, a parasite of the pike, alive for a month in 

 a slightly acid pepsin-peptone solution containing from 3 to 4 

 per cent, of nutritive matter, and less than 1 per cent, of 



NaOl. 



The methylen blue Mr a vitam staining method should bo 



found useful with this group. 



833. Trematodes (FISCHER, Zeit. f. wiss. Zool., 1884, p. 1). 

 Opisthotrema cochleare may be mounted entire in balsam, after 

 treatment with absolute alcohol, picro-carmine, or haema- 

 toxylin or ammonia-carmine, and clearing with clove oil. 

 For sectioning, Fischer recommends imbedding in a mass 

 made by dissolving 15 parts of soap in 17'5 parts of 96 per 



