338 



CYTCXTHEMICAL TESTS ON EMBRYOS 



The glutathione is partially soluble, hence the reaction will vary with fixation and 

 other preliminary treatments. Fresh material, without fixation, gives even more 

 reliable results. 



Fix oocytes in trichloracetic acid for 10 minutes, wash in distilled water, place in 

 5% zinc acetate for a few seconds, and wash again in distilled water. Treat with 

 10% aqueous sodium nitroprusside plus a few drops of NH4OH, and mount in glycer- 

 ine under a coverslip. 



E^XRLY BLASTULA 



GASTRULA 



Distribution of -SH proteins 

 (nitroprusside test) at the 

 beginning (a) and end (b) of 

 oogenesis. (Redrawn from 

 Brachet, 1944). 



The distribution of basophilic granules (dots) 

 and the sulfhydril proteins (dashes) (after 

 Bmchet, 1938). 



Location of the -SH proteins by the nitroprusside test during vorious stages in the 

 early development of the amphibian embryo. (Redrawn from Brachet, 1944) 



