448 WILSON. [Vol. XI. 



most favorable specimens, they are found to be granular in 

 structure as if composed of a string of beads. ^ At their base 

 this appearance is less obvious, and sometimes cannot be 

 distinguished ; but as they pass outward, the granular structure 

 becomes more obvious, until at their tips, where they branch 

 out into the general reticulum, they become quite indistin- 

 guishable from the latter (Fig. I, B, C). 



As the pronucleus advances the rays rapidly extend them- 

 selves, and may be traced far out into the egg-substance, where 

 they are lost in the general reticulum as in the earlier stages. 

 The central mass meanwhile greatly increases in size (Phototype 

 3). Upon coming in contact with the egg-nucleus the central 

 mass of the aster flattens somewhat against it and then rapidly 

 extends itself so as to lie like a cap upon one side of it. The 

 mass thus formed is of a horse-shoe shape in section, with a 

 somewhat irregular contour (Phototype 4, Text-figs. II, III), 

 from which radiate extremely long and conspicuous rays 

 throughout nearly an entire hemisphere of the ^gg. The 

 structure of the rays at this period is essentially the same as 

 that in the earlier stages, but may be even more clearly made 

 out. At their base they pass directly into, and are lost in, the 

 central mass. At their outer ends they break up into the 

 general reticulum. Careful examination shows further that 

 they branch in their middle portions so that the number of 

 rays continually increases towards the outer portion of the 

 aster as described long since by Van Beneden. In their 

 middle portions they have a wavy or sometimes even a zig-zag 

 course, and the branching of the rays seems always to take 

 place from one of the angles. Toward their bases the rays 

 often appear as quite continuous fibres ; in their middle 

 portions they are less regular and sometimes beaded in appear- 

 ance ; toward their outer portions they often show in the 

 clearest manner that they are composed of rows of blue-staining 

 granules closely similar to those of the general reticulum, but 

 as a rule somewhat smaller. 



B. Fusion of the Nuclei and Fissiojt of tJie Aster. — The 



1 Cf. Van Beneden and Neyt, Nouvelles recherches, etc., Btill. de VAcad. Roy. 

 de Belgiquc^ III, 14, 1S87, p. 266. 



