218 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
give a correct idea of this “Schaumwerk " structure, if one imagines the 
yolk granules many times smaller and the protoplasmic films much more 
slender than in the egg of Distaplia as represented by Davidoff. 
The ventral hemisphere also is filled with yolk granules, but here the 
protoplasmie packing between them is more abundant and less uniformly 
distributed. It is most conspicuous at the surface, where it forms a 
thin layer nearly free from yolk granules spreading over almost the 
whole hemisphere. Within this layer it fades away gradually, but 
often, as in the case figured (Fig. 1), again becomes prominent at a little 
deeper level as a series of irregular blotches among the yolk granules ; 
then it once more grows fainter toward the centre of the egg, attaining 
the condition described for the dorsal hemisphere. 
The presence of a spermatozoón cannot be detected in the eggs of this 
lot. In those of Series B, lot 3, however, its influence is clearly visible. 
(Seo Figs. 2 and 4.) About fifteen minutes is estimated to have 
elapsed between the stage just discussed and the one here presented. 
At this stage we see in the ventral hemisphere, at some point just 
beneath tho surface, a spherical region entirely free from yolk granules. 
(See Fig. 2.) Its central portion is occupied by a finely granular sub- 
stance, which stains in heematoxylin an intense blue, shading off some- 
what gradually into the more faintly and lightly colored protoplasm 
occupying the outer portion of the area and continuous with the sim- 
ilarly stained films of the Schaumwerk, At one point the yolk-free re- 
gion extends out to the surface of the egg. ‘This probably represents the 
place of entrance of the spermatozoón, which we have reason to believe 
produces the clear area. The deeply staining substance at the centre of 
this area is tho male archoplasm or attraction sphere. Tt is undoubtedly 
similar in nature, as it is in optical appearance, to the darkly stained 
substance seen at the deep end of the maturation spindle in Figure I, and 
which may therefore be called the female archoplasm. The male pro- 
nucleus cannot be made out in the egg a portion of which is shown in 
Figure 2. In other eggs of the same lot, however, it can be clearly seen ; 
for example, in Figure 4, which represents a stage a little more advanced 
than the one seen in Figure 2. The arca free from yolk is seen in Figure 4 
to have enlarged somewhat; the attractive influence of tho archoplasm 
at its centre has manifestly been extended over the greater portion of the 
hemisphere in which it lies. This fact is indicated diagrammatically by 
the dotted lines in the figure, They are meant simply to indicate that 
those films of the protoplasmic Schaum werk which run radially with 
reference to the attraction sphere have become thicker and more promi- 
