388 EMBRYOLOGY 



concentrated hydrochloric acid, and a knife pointful of pepsin (it is 

 not necessary that all the pepsin should be dissolved). The ova 

 may then be treated with alcohol, oil of bergamot, and paraffin, 

 and (with some exceptions, amongst which is Bomhijx mori) will 

 be found to cut without crumblincr. 



849. Diptera (Henking, Zeit. wiss. Zool., xlvi, 1888, p. 289). 

 Ova still contained within the fly may be fixed by plunging the 

 insect for some time into boiling water, then dissecting out and 

 bringing them into 70 per cent, alcohol. Laid eggs may have 

 boiling water poured over them, or be put into solution of 

 Flemming in a test-tube which is plunged into boiling water until 

 the eggs begin to darken (about a minute). Cold solution of 

 Flemming easily causes a certain vacuolisation pf the contents of 

 the ova. Open the ova at the larger end, stain with borax- 

 carmine for fifteen to thirty hours, and cut in paraffin. 



Bruel {Zool Jahrh., Abth. Morph., x, 1897, p. 569) fixes larvae 

 and pupae in absolute alcohol heated to 70° to 75° C, and con- 

 taining a " little " sublimate. See also Van Rees, ibid., iii, 

 1888, p. 10. 



Bengtsson {Handl. Fysiogr. Scdlsk Lund., viii, 1897) finds hot 

 alcoholic solution of sublimate (Frenzel's, § 74) the best fixative 

 for larvas of Phalacrocera. He could not succeed in softening the 

 chitin with eau de Javelle. 



Perez {Arch. Zool. ex-per., (4), v, 1910, p. 11) fixes pupae in 

 Bouin's picro-formol, or Marchoux's mixture, for twenty-four 

 hours , 



850. Lepidoptera (Bobretzky, Zeit. zviss. Zool., 1879, p. 198). 

 Ova are slightly warmed in water and put for sixteen to twenty 

 hours in 0-5 per cent, chromic acid. The membranes can then 

 be removed. 



851. Hymenoptera. Carriere and Burger {Nova Acta Acad. 

 Leop. Car., Ixix, 1897, p. 273) kill ova of Chalicodoma by warming 

 in water to 60° C, and fix in aqueous picric acid, or alcohol of 

 70 per cent. 



Petrunkewitsch {Zool. Jahrh., Abth. Morph., xiv, 1901, 

 p. 576) fixes for twenty-four hours in his sublimate mixture, and 

 passes into alcohol of 70 per cent, with iodine. 



852. Orlhoptera (Patten, Quart. Journ. Mic. Sci., 1884, 

 p. 549). The ova or larvae (of Blattidae) are placed in cold water, 

 which is gradually raised to 80° C. You leave off heating as soon 

 as the ova have become hard and white. Pass very gradually 

 through successive alcohols, beginning with 20 per cent. 



Wheeler {Journ. of Morph., iii, 1889, p. 292) dissects out 

 ovarian ova in salt solution and fixes in liquid of Perenyi (fifteen 

 minutes), then treats with alcohol, and stains with borax-carmine. 

 Laid eggs may be killed by Patten's method. After heating, the 

 two lips of the crista of the capsule may be separated with fine 



