EMBRYOLOGICAL METHODS. 351 



paraffin, and (with some exceptions, amongst which is Bombyx 

 mori) will be found to cut without crumbling. 



The contents of fresh ova may conveniently be studied by 

 means of the following fluid : 



Distilled water . . . . 80 c.c. 

 Glycerin . . . -.. 16 



Formic acid . . . . 3 



1 per cent, osmic acid. .. '. 1 

 Dahlia . . . . ,. 0'04 grm. 



The eggs are simply teased in a drop of the liquid, and a 

 cover-glass put on. If it be desired to preserve the prepara- 

 tion, nothing more is necessary than to lute the cover-glass. 



626. Diptera (HENKING, Zeit. f. wiss. Zool, xlvi, 1888, 

 p. 289 ; Zeit. /. wiss. Mik., 1889, p. 59). Ova still contained 

 within the fly may be fixed by plunging the animal 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 of 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. 



See also (for Chironomus) RITTER, Zeit. f. wiss. Zool., i, 

 1890, p. 408; Zeit.f. wiss. Mik., viii, 1, 1891, p. 87 (strings 

 of ova fixed with hot 30 per cent, alcohol containing a little 

 sublimate, and stained in the mass by immersion for several 

 days in picro-carmine). 



BRUEL (Zool. Jahrb., Abth. Morph., x, 1897, p. 569) fixes 

 larvae and pupae in absolute alcohol heated to 70 to 75 C., 

 and containing " a little " sublimate. See also VaN REES, 

 ibid., iii, 1888, p. 10. 



BENGTSSON (Handl. Fysiogr. 8aellsk. Lund., viii, 1897) finds 

 hot alcoholic solution of sublimate (Frenzel's, 70) the best 

 fixative for larvae of Phalacrocera. He could not succeed in 

 softening the chitin with eau de Javelle. 



627. Lepidoptera (BOBRETZKY, Zeit.f. wiss. 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 mem- 



