280 EMBRYOLOGICAL METHODS. 



609. KOLLMANN'S Fixative (KOLLMANN, Arch. Anat. Phys., 1885, 

 p. 296). 



Bichromic of potash .... 5 per 100. 

 Chromic acid . . . . . 2 ,, 

 Concentrated nitric acid . . 2 ,, 



For ova of Teleostea. Fix for twelve hours, wash with water for 



twelve hours, then remove the chorion, and put the ova into 70 per cent. 



alcohol. 



610. RABL'S Method, see 587 ; for KOWALEWSKY'S see Zeit. wiss. 

 Zool, xliii, 1886, p. 434, or Third Edition. 



611. Salmonidae. HENNEGUY'S methods have been given, 609. 

 KOPSCH (Arch. mik. Anat., li, 1897, p. 184), on the suggestion of 



VIRCHOW, fixes embryos for five or ten minutes in a mixture of 

 1 part of chromic acid to 50 of glacial acetic acid and 450 of water, 

 then removes into chromic acid of 1 : 500, and as soon as may be 

 removes the capsule and yolk under salt solution, and completes 

 the hardening in the chromic acid or the saturated sublimate 

 solution. 



Similarly, BEHRENS (Anat. Hefte, x, 1898, p. 233). He opens 

 the ova in the salt solution from the antipolar side, and frees the 

 embryo from the yolk that remains by blowing the latter away with 

 a fine-pointed glass tube. 



Similarly also SOBOTTA (ibid., 1902, p. 579). 



GUDGER (Proc. U.S. Nation. Mus., xxix, 1906, p. 448) fixes 

 blastoderms in fresh liquid of Perenyi, which does not make the 

 yolk too hard ; later stages in WORCESTER'S liquid (9 parts of 

 saturated solution of sublimate in formol of 10 per cent, and 1 part 

 of acetic acid), for half an hour to an hour, and brings gradually 

 into alcohol of 70 per cent. 



BOUIN (C. R. Soc. Biol, Iv, 1903, p. 1691) fixes for thirty-six to 

 forty-eight hours in picro-formol. 



EABL-KUCKHARD'S Method (Arch. Anat. Entw., 1882, p. 118). Fix in 

 10 per cent, nitric acid for fifteen minutes. Kemove the membranes to 

 avoid deformation of the embryos, and put the ova back into the acid 

 for an hour. Wash out in 1 to 2 per cent, solution of alum for an hour 

 and harden in alcohol. 



Modification of this method by GORONOWITSCH (see Morph. Jahrb., x, 

 1884, p. 381). 



612. Selachia. BEARD (Anat. Anz., xviii, 1900, p. 556) has 

 found that the best fixatives for embryos of Raja are Rabl's picro- 

 platinic mixture, 587, and sublimate. 



Living embryos can be observed by scraping the shell thin with a 

 knife (KASTSCHENKO, Anat. Anz., iii, 1888, p. 445, and His, Arch. 



