314 EMBRYOLOGICAL METHODS. 



into Miiller's solution. Open them therein with fine scissors 

 the vitellus, which immediately coagulates on contact with air, 

 dissolves, on the contrary, in Miiller's solution and the germ 

 and cortical layer can be extracted from the capsule of the 

 ovum. They should be left in clean Miiller's solution for a 

 few days, then washed with water for twenty-four hours, and 

 brought through successive alcohols. 



Another method is as follows : The ova are fixed in solution 

 of Kleinenberg containing 10 per cent, of acetic acid. After 

 ten minutes they are opened in water containing 10 per cent, 

 of acetic acid, which dissolves the vitellus. The embryos are 

 put for a few hours into pure solution of Kleinenberg, and 

 are then brought through alcohol of gradually increasing 

 strength. 



605. KOLLMANN'S Method (see 40). 



606. PEBENYI'S Method (see 39). 



607. KOWALEWSKY'S Method (Zeit. f. wiss. Zool., xliii, 1886, p. 434)* 

 Fix for an hour and a quarter in a mixture of 8 volumes of picro-sulphuric 

 acid with one of 1 per cent, chromic acid. Wash out for twelve hours with 

 20 per cent, alcohol, and pass the ova very gradually through alcohol of 20, 

 28, 35, 43, 50, 60, and 70 per cent, strength', the last to be changed frequently 

 until all the picric acid is extracted. Before staining, the capsules of the 

 ova should be opened. Stain with borax-carmine or hsematoxylin, and im- 

 bed in paraffin. 



608. BOYEE'S Methods. See Bull. Mus. Comp. ZooL, Harvard, xxiii, 

 1892, p. 93 ; Journ. Eoy. Mic. Soc., 1892, p. 699. 



609. RABL-KUCEHABD'S Method (Arch.f. Anat. u. Entw., 1882, p. 67). 

 Fix in 10 per cent, nitric acid for fifteen minutes. Eemove the mem- 

 branes 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 GOEONOWITSCH (see Morph. Jahrb., x, 

 1884, p. 381). 



610. Pelagic Fish Ova (WHITMAN'S method ; Amer. Natural., xvii, 

 1883, pp. 1204-5 ; Journ. Eoy. Mic. Soc. [N.S.], iii, 1883, p. 912, and 

 Methods of Research, &c., p. 152). Fix by treatment first for five to ten 

 minutes with a mixture of equal parts of sea water and ^ per cent, osmic 

 acid solution, and then for one or two days with a modified Merkel's solution 

 (due to Eisig), consisting of equal parts of 0'25 per cent, platinum chloride 

 and 1 per cent, chromic acid. Prick the membrane before transferring to 

 alcohol. Whitman found that the usual Merkel's fluid caused maceration of 

 the embryonic portion of the egg. Picro-sulphuric acid causes the embryonic 

 cells to swell, and in many cases to become completely disorganised. The 



