342 CHAPTER XXVI. 



fixed with solution of Flemming, for fifteen to thirty minutes 

 in it. Some other means of attaining the same end are 

 given in the following paragraphs. 



A great difficulty with the ova of Amphibia lies in their 

 becoming extremely brittle on imbedding in paraffin. 

 CARNOY and LEBBUN (La Cellule, xii, 1897, p. 212) fix 

 ovaries or ovarian ova for fifteen minutes to three quarters 

 of an hour in Gilson's mercuro-nitric fluid, 70, and .pre- 

 serve them in 80 per cent, alcohol. To imbed, they are 

 brought for a quarter of an hour into 95 per cent, alcohol, 

 five minutes in absolute alcohol, then into a mixture of 

 alcohol and chloroform in equal parts, and as soon as they 

 sink in that they are put into pure chloroform. Paraffin is 

 added to the chloroform, enough to about double the 

 volume of the whole, and the whole is put for about three 

 hours into a stove at 35 "C. Lastly, the ova are put for 

 not more than Jive minutes into a bath of pure paraffin at 

 52 C. ' 



See also MORGAN, Devel. of the Frog's Egg, New York, 1897, p. 171. 



601. Axolotl. The ova are easier to prepare than those 

 of the Anura, because the yoke 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. 



602. Triton "(ScoTT and OSBORN, Quart. Journ. Mic. Soc., 

 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. 



HEKTWIG (Jen. Zeit. f. Naturw., 1881-2, p. 291) puts the 

 eggs into a mixture of equal parts of 2 per cent, acetic acid 

 and 0'5 per cent, chromic acid. After ten hours he incises 

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

 turns out the embryos and brings them into successive 

 alcohols. 



BKAUS (Jena Zeit., xxix, 1894, p. 443) fixes ova to a 



