54 J- F - McCLENDON. 



removal from the tube, the eggs must be fixed in fluids which 

 cause them to draw away from the chorion (partly by increasing 

 the osmotic pressure inside the chorion) and which do not make 

 them friable. The only fluids which served contained alcohol 

 and nitric acid. Nitric acid of 5 per cent.-io per cent, in alcohol of 

 about 30 per cent, served well enough for cell lineage but allowed 

 the chromosomes to swell (partly re-dissolve in water ?). The 

 addition of chromic acid (Perenyi's formula) prevented the swell- 

 ing of the chromosomes and made a good fixitive if manipulated 

 properly. The chromic acid in this mixture is changed to blue 

 chromic oxide, and P. Mayer in the first German Edition of Lee's 

 " Vade Mecum," ' says it contains 30 per cent, alcohol, 5 per cent, 

 nitric acid and a little nitric ether and chromic oxide, the last two 

 having no effect in fixation. However, it has been my experi- 

 ence that the chromic oxide was necessary to prevent swelling 

 of the chromosomes. Fischer ('99) says that nucleinic acid is 

 not precipitated by dilute nitric acid, and that its precipitate 

 formed by alcohol is soluble in water. It is possible that the 

 swelling of the chromosomes is due to the solution of nucleinic 

 acid or its compounds in the aqueous staining bath. In addition 

 to its other qualities, nitric acid bleaches the eggs of Pandarus, 

 and others that contain pigment, and although it is difficult to 

 wash out (in 70 per cent, alcohol) it was found to be an indis- 

 pensable ingredient. 



I tried various standard fixatives for eggs to be sectioned, and 

 found them little better than Perenyi's fluid ; but for whole adults 

 to be sectioned for the ovaries, etc., the latter fluid seemed to be 

 much inferior to some others. It was probably too much diluted 

 by the body fluids. 



For staining whole eggs Delifield's hsmatoxylin diluted and 

 acidulated (Conklin's formula) was the most convenient, but for 

 sections various stains were used. In Hermann's safranin-gen- 

 tian violet, besides the usual differentiations of chromatin, the 

 centrosomes (centrioles) stained red and the archoplasm blue 

 (unless the sequence of stains was reversed). Iron ha^matoxylin 

 g-ave the sharpest stains for chromosomes. 



It is probable that there can be no fixation without some 



1 " Grundziige der Mikroskopischer Tecknik," by Lee and Mayer, Berlin, 1898. 



