EMBRYOLOGICAL METHODS. 345 



Bichromate 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. 



608. RABL'S Method (see 587). 



609. KOWALEWSKY'S Method (see Zeit.f. wiss. ZooL, xliii, 1886, p. 434, 

 or Third Edition). 



610. Salmonidae. HAKKISON (Arch. mik. Anat., xlvi, 1895, 

 p. 505) fixes embryos of Salmo in saturated solution of 

 sublimate in 5 per cent, acetic acid. 



FELIX (Anat. Hefte, 1 Abth., viii, 1897, p. 252) fixes the 

 ova for three quarters of an hour in acetic sublimate, but 

 dissected-out embryos in liquid of Zenker, the vitellus being 

 removed from the abdominal cavity with a brush. 



KOPSCH (Arch. mik. Anat., li, 1897, p. 184), on the sug- 

 gestion of VIRCHOW, fixes the 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 them 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 saturated sublimate solution. 



Similarly BEHRENS (Anat. Hefte, H. 32, 1898, p. 227 

 Zeit. f. wifts. Mik., xv, 1899, p. 332). He leaves the ova for 

 about an hour in the chromic acid, not much more anyway ; 

 he opens them 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 ; after which 

 the embryo can be easily detached from the capsule. It is 

 then removed for about three hours into a mixture of 1 part 

 saturated picric acid solution, 1 part saturated sublimate 

 solution, and 2 parts distilled water, after which it is treated 

 in the usual way with iodine and successive alcohols. 



611. RABL-RUCKHABD'S Method for Salmonidse (Arch. f. Anat. u. 

 Entw., 1882, p. 118). Fix in 10 per cent, nitric acid for fifteen minutes. 

 Remove 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 GOBONOWITSCH (see Morph. Jahrb., x, 

 1884, p. 381). 



