348 CHAPTER XXVI. 



picro-sulphuric acid and 2 per cent, solution of bichromate of 

 potash in equal parts, and after one or two minutes incises 

 them in the equator, fixes for an hour and a half in picro- 

 sulphuric acid the halves that contain the formative vitellus, 

 separates this from the nutritive vitellus with a spatula, 

 spreads it out, and hardens it in alcohol of 70 to 90 per 

 cent. He fixes entire ova in liquid of Flemming or osrmc 

 acid. 



KORSCHELT (Festschrift Leuckart, Leipzig, 1892, p. 348) 

 fixes advanced embryos of Loligo in liquid of Flemming, 

 sublimate, picro-sulphuric acid, or 0'2 per cent, chromic acid. 

 This last is specially good for young embryos if it is washed 

 out with many changes of picric acid. 



620. Gastropoda (HENNKGUY). Ova of Helix may be fixed 

 for from four to six hours in Mayer's picro-nitric acid. 

 The carbonate of lime that encrusts the external membrane 

 is thus dissolved, and the albuminous coat of the egg is 

 coagulated. The egg is opened with needles, the albumen 

 conies away in bits, and the embryo can be removed. Treat 

 with successive alcohols, and imbed in paraffin. 



Miss A. HENCHMAN (Bull. Mu*. Comp. Zool., Harvard, xx, 

 1890, p. 171; Journ. Roy. Mic. Soc., 1891, p. 274; Zeit. f. 

 wiss. Mil:., viii, 2, 1891, p. 216) fixes ova of Lirnax with 

 0'33 per cent, chromic acid, or with liquid of Perenyi. It 

 is best to remove only the outer envelope before putting 

 into the chromic acid, the inner membrane being removed 

 after two or three minutes therein. Where Perenyi is used 

 the membranes must be removed first, as the albumen Avill 

 else coagulate in such a way as to prevent the removal of 

 the embryos. For the manner of obtaining the ova, see 

 previous editions. 



MKISKNHKIMKR (Zeit. iviss. Zool., Ixii, 1896, p. 417) dissects 

 out the embryos of Limax and fixes them Avith picro-sulphuric 

 acid or concentrated sublimate. Advanced embryos are 

 first got into extension by means of 2 per cent, cocain, or 

 are rapidly killed with hot sublimate. 



SCHMIDT (Entw. Pulmonaten, Dorpat, 1891, p. 4) fixes the 

 ova in toto with concentrated sublimate, and dissects them 

 out afterwards. 



Similarly KOFOID (Bull. Mus. Harvard Coll., xxvii, 1895, 



