METHODS FOll INVERTEBRATES. 471 



drates rapidly, clears with cedar or bergamofc oil, and mounts 

 in balsam. Nematocytes blue, tlie rest unstained. 



901. Actinida. — For narcotisation methods see §§ 15 to 26. 



902. Fixation. — In Le Atdnic, Fauna u. Flora d. Golfes v. 

 Neapal, Andees says that hot corrosive sublimate often gives 

 good results. In the case of the larger forms the solution 

 should be injected into the gastric cavity. 



Freezing sometimes gives good results. A vessel contain- 

 ing Actinia) is put into a recipient containing an ice-and-salt 

 freezing mixture and surrounded by cotton-wool. After 

 freezing, the block of ice containing the animals is thawed 

 in alcohol or some other fixing liquid. 



Dqeeden [Journ. Inst. Jamaica, ii, 1898, p. 449) narcotises 

 with magnesium sulphate, § 24, and fixes with forraol of 3 

 to 5 per cent. 



903. Maceration. — For the Heetwigs' method [Jen. Zeit., 

 1879, p. 4.57) see § 534. The tissues should be left to 

 macerate in the acetic acid for at least a day, and may then 

 be teased in glycerin. 



List [Zeit. loiss. Mile, iv, 1887, p. 211) treats tentacles of 

 Anthea cereus and Sagartia parasitica for ten minutes with 

 a mixture of 100 c.c. of sea water with 30 c.c. of Flemniing's 

 strong liquid, then washes out for two or three hours in 

 0"2 per cent, acetic acid, and teases in dilute glycerin. 

 Picro-carmine may be used for staining. 



904. Nervous system. — This group is generally held to be 

 refractory to the Golgi impregnation. Havbt, however [La 

 Cellule, xviii, 1901, p. 388), has obtained good i-esults by the 

 rapid method on young specimens of Metridium dianthus. 

 Besides nerve-cells, there are impregnated neuro-muscular 

 cells, gland-cells, and nematocytes. Leave for o to 8 days 

 in the osmic micture. He has also had good results by the 

 intra vitam methylen blue method (this is also good for 

 nematocytes). So also has Geqselj [Arb. Zool. Inst. Univ. 

 Wien, xvii, 1909, p. 269), adding the dye to the water with 

 the animals till it gives a steel-blue tint. 



