302 CHAPTER XXV. 



606, Salamandra (RABL, Morphol. Jahrb., xii, 2, 1886, p. 252). 

 For his more recent methods see 587. 



G-KONROSS (Anat. Anz., xiv, 1898, p. 461) fixes the ova with 

 a mixture of 50 parts each of saturated sublimate and 0'5 

 per cent, chromic acid with one part of acetic acid. 



607. Rana (0. HERTWIG, Jen. Zeit. Naturw., xvi, 18S3, 

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

 to 96 C.) for five or 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, chromic 

 acid for not more than twelve hours, or into alcohol of 70, 

 80, and 90 per cent. Chromic acid makes ova brittle and 

 attacks the pigment, whilst alcohol preserves it, which is 

 frequently important for the study of the germinal layers. 



MORGAN (Anier. Nat., xxv, 1891, p. 759, and Derel. of 

 the Frog's Egg, 1897, p. 171) has the following. During 

 the periods in which it is difficult or impossible to remove 

 the inner jelly-membrane the eggs can be freed as follows : 

 Each egg is cut out with scissors from the general jelly-mass, 

 and put for from one to twelve hours into saturated solution 

 of picric acid in 70 per cent, alcohol containing 2 per cent, of 

 sulphuric acid. Wash in several changes of alcohol of 70 per 

 cent. About the second day in this the inner membrane 

 begins to swell, and on the third or fourth day may be 

 pierced by a needle, and the egg removed and placed in 80 

 percent, alcohol (see also WHITMAN, Metli. of Research, p. 156). 



SCHULTZE (Arch. mik. Anat., Iv, 1899, p. 174) removes 

 with scissors the outer layers of albumen, and puts the ova 

 for five minutes in 2 per cent, formol warmed to 75 or 

 80 C. The membrane left on the ova then rises up suffi- 

 ciently to allow the ova to be got out with needles. 



See also BORN (ibid., xliii, 1894, p. 1). 



KING (Journ. Morph., xvii, 1901, p. 295, and xix, 1908, p. 

 370) fixes (for a few minutes) the spawn (of Bufo) in sublimate 

 (saturated with 5 per cent, of acetic acid), or in Flemming, 

 Zenker, or Hermann, brings into alcohol, first of 50 and then 

 80 per cent., and removes the jelly after a few days. 



BLES (Trans. Roy. Soc. Edinburgh, -xli, 1905, p. 792) takes 

 for ova formol of 10 per cent., but for embryos and larvre 

 the mixture given 109, 



