268 EMBRYOLOGICAL METHODS. 



imbed in paraffin or celloidin, collodionising the sections 

 (HENNEGUY). 



565. Triton (Scora and OSBOEN, Quart. Journ. Mic. 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. 



566. Triton (HERTWIG, Jen. Zeit. f. Naturw., 1881-2, p. 

 291). Put the eggs into a mixture of equal parts of 2 per 

 cent, acetic acid and 0'5 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 suc- 

 cessive alcohols. 



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

 252). Fix in chloride of platinum of 0'25 to O3 per cent., 

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

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

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



568. Rana (O. 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 

 makes ova brittle ; they ought not to remain in it for more 

 than twelve hours. Chromic acid destroys or attacks the 

 pigment of the ova, whilst alcohol preserves it, which is fre- 

 quently important for the study of the germinal layers. 



569. Whitman's Method (Meth. of Research, 1885, p. 156). 

 Osmic acid of 0'25 per cent, twenty minutes. Chromo- 

 platinic mixture ( 575) twenty-four hours. Water two hours. 

 Alcohol. Borax-carmine. 



570. Schultze's Method (Zeit. f. wiss. ZooL, v, 1887, p. 177). 

 Flemming's mixture, twenty-four hours. Water. Alcohol 

 50 per cent, twenty-four hours ; 70 per cent, ditto ; 85 per cent, 

 ditto ; 95 per cent, ditto ; the last to be frequently changed. 

 The ova passed through turpentine into paraffin. If the ova 



