No. 3-] EGG OF ALLOLOBOPHORA FCETIDA. 527 



digestion fluid. For example, in one section of an ovary we 

 would find that in some cells only the chromatin had disap- 

 peared ; in others the cell membrane or nuclear membrane, 

 or both, would succumb first to the action of the pepsin, and 

 some of the cells would disappear completely ; in others part 

 of the cytoplasm was lost, while the membrane of the cell and 

 nucleus remained intact. As a rule, the nucleoli and archo- 

 plasm (yolk-nucleus) show the strongest resistance to the action 

 of the digestion fluid, this possibly being due to their relative 

 density. 



To test the suspicion that these results might be caused by 

 maceration due to the warm hydrochloric solution, a slide was 

 subjected to the same technique, omitting the pepsin, but no 

 effect was produced upon the preparation, even after six hours' 

 treatment. In order to ascertain as nearly as possible the 

 exact effect of the digestion fluid, we adopted the following 

 method : After mounting an unstained preparation in xylol, 

 xylol balsam, or glycerine,^ we selected a small oocyte show- 

 ing cytoplasm, yolk-nucleus, and nucleolus ; and this we pho- 

 tographed at a magnification of 660 diameters, the same cell 

 being photographed again after treatment with the digestion 

 fluid. By a persistent repetition of this method we reached 

 a pretty definite conclusion as to the inconstancy of the action 

 of the pepsin and how far this inconstancy invalidates it as a 

 precise test. 



At first we selected and^ photographed more than one cell 

 in each preparation, but the unequal rapidity of the action 

 of the pepsin made this impracticable, for one cell often 

 entirely disappeared before the other showed any response 

 to the digestion fluid. After photographing the unstained 

 cell, the slide was put in the digestion fluid at a temperature 

 of 40° C. and examined every thirty minutes (under a 2 mm. 

 immer. lens), comparing the cell with the negative. It is thus 

 possible to follow each step in the process, and to determine 

 positively just which structures show the least resistance to the 

 digestion fluid, and also possibly whether digestion is the only 



1 The action of the digestion fluid was not impeded by previous mounting in 

 glycerine, xylol, or xylol balsam. 



