EMBRYOLOGY 383 



GuDGER {Proc. U.S. Nation, Mm., xxix, 1906, p. 448) fixes 

 blastoderms in fresh liquid of Perenyi, which does not make the 

 yolk too hard ; later stages in Worcester's liquid (9 parts of 

 saturated solution of sublimate in formol of 10 per cent, and 

 1 part of acetic acid), for half an hour to an hour, and brings 

 gradually into alcohol of 70 per cent. 



Bouix (C. R. Soc. Biol., Iv, 1903, p. 1691) fixes for thirty-six to 

 forty-eight hours in picro-formol. 



Rabl-Ruckhard's Method (Arch. Anat. Enhv., 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 Goronowitsch (see Morph. Jahrb., x, 

 1884, p. 381). 



835. Selachia. Beard {Anal. Anz., xviii, 1900, p. 556) has 

 found that the best fixatives for embryos of Raja are Rabl's 

 picro-platinic mixture, § 80, and sublimate. 



Living embryos can be observed by scraping the shell thin 

 with a knife (Kastschenko, Anat. Anz., iii, 1888, p. 415, and 

 His, Arch. Anat. Phys., Anat. Abth., 1897, p. 3). See also Braus, 

 Morph. Jahrb., xxxv, 1906, p. 250. 



836. Amphioxus. Sobotta {Arch. mik. Anat., 1. 1897, p. 20) 

 fixes for twenty-four hours in liquid of Flemming ; Hatschek 

 {Arb. Zool. Inst. Wien, iv, 1881) in picro-sulphuric acid. Impregna- 

 tion takes place in the evening, and segmentation is completed 

 during the night. 



Leoros [Grundzuge, Lee and Mayer, 1910, p. 288) fixes ova 

 and embryos in equal parts of formol and Flemming. Sublimate 

 is not good ; Rabl's mixtures are better. Larvae and young 

 animals ought first to be anaesthetised with cocaine in sea-water. 

 After fixation they should remain only for as short a time as 

 possible in alcohol. 



Cerfoxtaine {Arch. Biol., xxii, 1906, p. 287) fixes with 

 Flemming or Hermann. For study of ova in toto he orients them 

 on a slide in clove-oil collodion which he sets with chloroform, 

 and adds balsam. For sectioning, he orients in the same way on 

 a layer of paraffin spread on a cover-glass and imbeds the whole 

 in paraffin. 



837. Pelagic Fish Ova. Whitman {Amer. Natural., xvii, 1883, pp. 

 1204^5 ; and Methods of Research, etc., p. 152). Fix by treatment first 

 for five to ten minutes with a mixture of equal parts of sea-water and 

 J per cent, osmic acid solution, and then for one or tAvo days with a 

 solution (due to Eisig) of equal parts of 0-25 per cent, platinum chloride 

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

 to alcohol. See also Agassiz and Whitiman, in Proc. Amer. Acad. Arts 

 and Sciences, xx, 1884 ; and Collinge, Ann. and Mag. Nat. Hist., x, 

 1892, p. 228. 



