614 INVERTEBRATES 



therefore easy to show up the mesogloea alone in red, and thus 

 display the anatomy advantageously. 



Sections may be thick or thin. Stain in borax carmine until 

 the mesogloea is fairly strongly stained, but everything else still 

 scarcely tinged. This takes from half an hour to several hours. 

 Wash in a stream of distilled water from a wash-bottle. Stain for 

 four minutes in Mayer's acid hacmalum. Blue. (No differentiation 

 is required.) Wash in distilled water. Dip for less than ten 

 seconds in | per cent, light green in 70 per cent, alcohol. Before 

 the ten seconds have elapsed, wash the stain off in a stream 

 of distilled water. Dehydrate at the ordinary speed. Mount 

 in balsam. Mesogloea, red. Nuclei, blue. Nematocysts, 

 green. 



For other narcotisation methods see §§17 to 26. 



1220. Fixation. In Le Attinie, Fauna u. Flora d. Golfes v. 

 Neapel, Andres 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 containing 

 Actiniae 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. 



DuERDEN {Journ. Inst. Jamaica, ii, 1898, p. 449) narcotises 

 with magnesium sulphate, § 23, and fixes with formol of 3 to 5 per 

 cent, 



1221. Maceration. P'or the Hertwigs' method {Jen. Zeit., 

 1879, p. 457) see § 568. 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. wiss. Mik., 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 Flemming'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. 



1222. Nervous system. This group is generally held to be 

 refractory to the Golgi impregnation. Havet, however {La 

 Cellule, xviii, 1901, p. 388), has obtained good results by the 

 rapid method on young specimens of Metridium dianthus. Besides 

 nerve-cells, there are impregnated neuro-muscular cells, gland- 

 cells, and nematocysts. He leaves for five to eight days in the 

 osmic mixture. He has also had good results by the intra-vitam 

 methylen blue method (this is also good for nematocysts). So 

 also has Groselj {Arh. Zool. Inst. Univ. Wien, xvii, 1909, p. 269), 

 adding the dye to the water with the animals till it gives a steel- 

 blue tint. 



