l6o GARDINER. [Vol. XI. 



pigment granules while the rest of the cell is free from them. 

 The action of these granules in the ova of PolycJiaenis is 

 apparently very similar, but unfortunately they are entirely 

 dissolved in alcohol, so that the history of their movements 

 within the cell is beyond reach by sections. Not infrequently, 

 while examining the surface of an ovum with an oil immersion, 

 I have seen one of these granules come up from within the 

 ovum to the surface, and move across the field of vision, but I 

 have never yet seen a granule pass from one cell into another ; 

 yet they disappear in some cells and later on appear in quantity 

 in others. When the ovum is so viewed it is clearly suggested 

 that there are wonderfully active forces at work within, for the 

 surface fairly scintillates with movements of the protoplasm 

 and these pigment granules. The manner in which the 

 granules are moved about from place to place indicates the 

 powerful nature of the force within. In regard to the dis- 

 appearance in one part of the ovum and reappearance in 

 another. Figs. 2, 3, 4, and 5 show these granules massed in 

 cells B, B', C and C, while later on these same cells (Figs. 1 1 

 and 12) are almost devoid of them, while on the directly 

 opposite pole of the ovum they are so crowded that the cleavage 

 lines are almost obscured. Fig. 13 shows the pole at which 

 the granules were first massed, and Figs. 14, 16, and 18 show 

 the opposite pole, which at an early stage was almost destitute 

 of color. Fig. 9 gives the appearance of this pole when the 

 granules first collect there, and also shows the color-effect pro- 

 duced when they are closely packed together. That the gran- 

 ules actually migrate from one cell to another seems impossible, 

 for, as is shown in Figs. 23, 24, and 25, the cells are bounded 

 by clear, distinct membranes through which the granules 

 would have to pass. It seems much more probable that they 

 fade out and become disintegrated in one part, while others are 

 organized in other parts. 



If an ovum is crushed they begin to fade almost immediately 

 and in a few minutes are no longer distinguishable. When 

 the segmenting ovum has reached the stage shown in Fig. 22 

 the pigmentation is almost confined to the few cells A, A', B^, 

 B'^, and £"3, E'^, and may be said to have reached its maxi- 



