310 CHAPTER XXV. 



He thinks that eau do. Jarelle for softening membranes is 

 best avoided. They should either be dissected away or left 

 in situ, and cut with the rest of the egg, according to the 

 nature of the case. To avoid brittleness of the yolk proceed 

 as follows : After fixing and treating with alcohol^ prick the 

 chorion and stain with borax-carmine. Put the stained ova 

 for twelve hours into a mixture containing 20 c.c. of 70 per 

 cent, alcohol, one drop of concentrated hj'drochloric acid, 

 and a knife pointful of pepsin (it is not nece.=sary 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 Boinhyx mori) will be 

 found to cut without crumbling. 



637. Diptera (Benkikg, Znt. uiss. Zool., xlvi, 1888, p. 289). 

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

 the animal for some time into boiling water, then dissecling 

 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 tlie 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 thii-ty 

 liours, and cut in paraffin. 



Bruef, [Zool. Jahrh.', Ahth. Morph., x, 1897, p. 569) fixes 

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

 and containing " a little " sublimate. Pee also Van Rees, 

 ihhh, iii, 1888, p. 10. 



Bengtsson {Eandl. Fysiogr. S ff 11 si: Lund., \ iii , 1897) finds 

 hot alcoholic solution of sublimate (Frenzel's, § 69) the best 

 fixative for larvae of Phalacrocera. He could not succeed in 

 softening the chitin with ean de Jarelle. 



Peeez [Arch. Zonl. c,r]ii'r., (4), v, 1910, p. 11) fixes pupa3 

 in Benin's picro-formol, or Marchoux's mixture, for twenty- 

 four hours. 



628. Lepidoptera (Bobeetzky, Zeit. uiss. Zool., 1879, p. 198). 

 — Ova are slightly warmed in wafer and put for sixteen to 

 twenty hours in 0'5 per cent, chromic acid. The membranes 

 can then be removed. 



