312 EMBRYOLOGICAL METHODS. 



diluted with 5 to 6 volumes of water, and leaves them there 

 till they can be shaken free, which happens (for Necturus) in 

 a few minutes. Blochmann takes eau de Javelle (potassium 

 hypochlorite), and dilutes it with 3 to 4 volumes of water, 

 and agitates the eggs, previously fixed with solution of 

 Flemming, for fifteen to thirty minutes in it. The ova are 

 afterwards preserved in alcohol in the usual way. Some other 

 means of attaining the same end are given in the following 

 paragraphs. 



599. Axolotl. The ova are easier to prepare than those of 

 the Anura, because the yolk is separated from the albuminous 

 layer by a wide space filled with a liquid that is not coagulated 

 by reagents. Put the eggs for a few hours into picro-sulphuric 

 acid, then pierce the inner chorion with fine scissors or needles, 

 and gently press out the ovum. Harden in alcohol. 



600. Triton (ScoTT and OSBORN, Quart. Journ. Hie. Sci., 

 1879, p. 449). The albumen is here present in the form of 

 several concentric coats, which are very delicate. Incise each 

 of them separately with fine scissors, turn out the ovum, and 

 fix it. Solution of Kleinenberg is the reagent that gives the 

 best results. 



601. Triton (HERTwiG,/e?i. Zeit.f. Naturw., 1881-2, p. 291). 

 Put the eggs into a mixture of equal parts of 2 per cent, 

 acetic acid and O5 per cent chromic acid. After ten hours 

 incise the membranes, opening one end of the inner chorion, 

 and turn out the embryos and bring them into successive 

 alcohols. 



602. Salamandra (RABL, Morphol Jahrb., xii, 2, 1886, p. 

 252). Fix in chloride of platinum of 0*25 to 0'3 per cent., 

 kept warm for from three to twenty-four hours, according to 

 the size of the embryos, wash well with water, treat with 

 successive alcohols, make sections, and stain on the slide. 



603. Rana (0. HEETWIG, Jen. Zeit. f. Naturw., xvi, 1883, 

 p. 249). The ova are thrown into nearly boiling water (90 

 to 96 C.) for five to ten minutes. The albuminous envelope 

 of the ovum is then cut open, and the ovum extracted under 

 water. The ova are then brought into 0*5 per cent, osmic 

 acid, or into alcohol of 70, 80, and 90 per cent. Chromic acid 



