^28 FOOT AND STROBELL. [Vol. XVII. 



factor that takes part in the process. Photo 24, PI. XLI, shows 

 a very young oocyte from an unstained preparation, before 

 treatment with the digestion fluid. The yolk-nucleus (archo- 

 plasm), the cell membrane, the cytoplasm, and the nucleolus 

 are shown. After securing a satisfactory negative of this cell, 

 the preparation was put for two hours in the digestion fluid 

 following the method above described. It was then stained 

 with iron-haematoxylin, mounted in balsam, and the same cell 

 again photographed (Photo 25). A careful comparison of the 

 two photographs will show that the cell membrane has com- 

 pletely disappeared and nearly all of the cytoplasm ; some of 

 the yolk-nucleus is also lost, but a large part of it still remains. 



Photo 26, PI. XLI, is a section through an older oocyte 

 showing archoplasmic masses (yolk-nucleus) scattered through- 

 out the cytoplasm. This was photographed from an unstained 

 preparation before treatment with the digestion fluid. It was 

 then placed in the warm digestion fluid for two hours, stained, 

 mounted, and re-photographed (Photo 27). These two photos 

 (26, 27) illustrate again the digestibility of the cytoplasm and 

 cell membrane, and show that the archoplasm is one of the last 

 constituents in the cell to yield to the action of digestion fluid. 

 Though many of the archoplasmic masses still remain intact 

 (Photo 27), both the chromatin and nuclear membrane have dis- 

 appeared, leaving no trace of a nucleus. It is possible that this 

 entire section of the nucleus may have dropped out, but varying 

 stages of disintegration of nuclei can be seen in the preparation. 



In a third preparation nothing was left of the photographed 

 cell after an hour and ten minutes in the digestion fluid. In 

 a fourth preparation, after thirty minutes, the cell membrane 

 and chromatin had disappeared, all other constituents remain- 

 ing intact.^ After forty additional minutes no perceptible 

 change had occurred ; after one hour additional (total, two 

 hours and ten minutes), the nuclear membrane and part of the 

 cytoplasm had disappeared ; the yolk-nucleus, nucleolus, and 

 chromatin were left untouched. 



1 This disappearance of the chromatin might be explained on the ground that 

 albumen is a constituent of chromatin. Fischer (7), p. 75, Wilson (31), 1900, 

 pp. 41 and 332. 



