TO THE EMBEYOLOGY OF AMPHIBIA. 41 



hour. This was then imbedded iii the usual celloidin-paraffin 

 method, care being taken that the egg should be thoroughly 

 permeated by celloidin by being kept two or three days in a 

 weak solution of it in a mixture of absolute alcohol and ether in 

 equal parts. 



After cutting and mounting, sections were stained on slides. 

 Most satisfactory results were obtained by subjecting them to 

 double- staining with the water solution of the acid fuchsin G 

 (ca 2°/o) and methyl-blue (ca o%). This is a slight modification 

 of Auerbach's method for the double-staining; of certain sexual 

 elements. A slide is placed in a solution of the first dye for 

 15-20 minutes, washed, and then put in a solution of the second 

 dye for 20-30 minutes. After a second washing, it is put into 

 absolute alcohol and the excess of blue colour is washed out by 

 stirring it with forceps. At a certain stage of discoloration, it 

 becomes very beautiful. The sections stained in this way show 

 the nucleus in blue, while the cytoplasm as well as the yolk- 

 spherules are red or reddish purple in colour. 



Fig. 51 is a cross-section passed through the approximate 

 center of a Rhacophoriis egg which is at about the stage repre- 

 sented in Fig. 8 and is intermediate between Figs. 20 and 21 of 

 Egg C. The segmentation cavity has not yet become enlarged to 

 its full extent, and its roof is still thick being composed of three 

 or four layers of cells. 



The next two figures are the median sagittal (Fig. 52), and 

 the middle transverse (Fig. 53), section of eggs corresponding to 

 the stage represented in Fig. 23 of Egg C. The segmenta- 

 tion cavity has now become enormously enlarged, and its roof 

 very thin, being composed of only two layers of cells (the epi- 



