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78 BOTANICAL GAZETTE [November 



an hour after fertilization. Subsequent work on marine animal 

 eggs has shown that the change in viscosity due to fertilization is 

 not so simple a phenomenon as one might think from what can be 

 observed in dissecting the egg of Focus. The protoplasm of the 

 ripe unfertilized egg is of comparatively uniform viscosity. Divi- 

 sion, following fertilization, brings on pronounced regional differ- 

 ences in consistency. In the egg these differences are wholly 

 obscured by the dense color of the chloroplasts. 



The changes in protoplasmic consistency which are a conse- 

 quence of fertilization can readily be determined in the dividing 

 echinoderm egg. The following data were obtained principally 

 from dissection of the ova of Tri pneustes , but were in great part 

 substantiated by subsequent work on the ova of Echinarachnius . 

 My observations on the viscosity of the echinoderm egg during 

 mitosis are less detailed than those of Chambers (6). In brief, 

 Chambers finds that the sphere (the central transparent area of 

 the aster of the mitotic figure) and the astral rays consist of a 

 clear liquid of very low viscosity, while the surrounding cytoplasm 

 is in the gel state, and that there is a "periodic reversal of the sol 

 to the gel state and vice versa" during mitosis. The following 

 data support, in the main, these findings of Chambers. 



The mature unfertilized sea-urchin egg is very viscous (v.v. 7) 

 and comparatively uniform in its viscosity. Following fertiliza- 

 tion a change in consistency soon takes place. With the first 

 appearance of the aster there is an increase in viscosity of the 

 peripheral cell cytoplasm. By peripheral protoplasm I refer to a 

 broad outer zone as distinct from an inner core, and not to an 

 ectoplasmic layer, a membrane, or the like. This increase in con- 

 sistency of the general peripheral protoplasm is from the very vis- 

 cous to the exceedingly viscous state. With the first appearance 

 of the amphiasters there is a pronounced decrease in viscosity of 

 the central region of the cell, and this condition is maintained 

 throughout the intermediate stages of divisions (from middle 

 prophase to late anaphase). Close examination shows that the 

 dilute protoplasm in the center of the mitotic figure makes up the 

 hyaline area surrounding each pole (the "hyaloplasm-sphere" of 



Wilson 28). 







