306 Trans. Acad. Sci. of JSt. Louis. 



nucleus and slipped out of its cytoplasmic envelope, large end 

 first, directly into the nucleus. The colorless coils c^Cy' are the 

 cytoplasmic envelope and lie entirely outside the nucleus. 

 The pointed end d of the sperm-nucleus has just escaped from 

 the cytoplasmic envelope. The fact that in this case at least 

 the entrance of the spermatozoid is effected large end first is 

 another evidence that the attraction which leads to entrance 

 is exerted between the nuclei. There certainly is not a com- 

 plete differentiation into an anterior and a posterior end at 

 this stage. These observations confirm the statement that 

 the prominent spermatozoids in figure 2 are entering large 

 end first — that is, that the sperm-nucleus responds directly 

 to the stimulus which draws it into the egg. 



After the sperm-nucleus has entered the egg-nucleus, the 

 fertilized nucleus shows a distinct tendency to develop a 

 smooth contour. The irregularity in the shape of the nucleus 

 begins to disappear. The changes which take place in the 

 sperm-nucleus are exceedingly diflScult to represent in detail. 

 Connection is made almost immediately with the nuclear net- 

 work of the egg. The surface of the sperm-nucleus begins 

 to appear granular as if the whole chromatin surface were 

 breaking up again into the separate granules of which it is 

 composed. This process does not follow in reverse order 

 the process of development, but the granules when first seen 

 are very fine and small like those of the egg chromatin. 



Figures 14, 15 and 16 are from successive sections of 

 another egg-cell where the spermatozoid has already entered 

 the nucleus leaving its cytoplasmic covering, c, figure 14, 

 outside the nucleus. These coils lie below the plane of the 

 drawing in figure 14 in the depression of the nuclear surface 

 which is shown so strikingly at d, figure 15. In figure 14 

 this funnel-like depression lies below the plane of the figure 

 and is overlaid by the nucleus. Its funnel-like character is 

 shown in figure 15, where it comes more nearly to a point 

 than in any other case observed. A comparison with figure 

 14 shows, however, that it lies in the side of the nucleus and 

 opens on one whole side instead of only at the mouth of the 

 funnel. The sperm-nucleus here shows considerable progress 

 in the process of disintegration. Numerous strands of 



