Thorn — Fertilization in Aspidium and Adiantum. 307 



nuclear network are seen leading out from it bearing chromatin 

 granules. The surface of the spiral itself has begun to show 

 granule-bearing strands disposed over a groundwork which in 

 some places appears to be homogeneous, in others shows 

 traces of a fibrillar structure. In the neck of the archegonium, 

 as shown in figure 16, a portion of the spermatozoid appears 

 broken into short segments. I have seen many spermatozoids 

 broken in this way. The segments formed in the various 

 cases when compared suggest that they represent structural 

 differences resulting in a characteristic mode of disintegration. 

 The same character appears in figure 22 where the breaking 

 of the segments has taken place after the entrance of the 

 sperm-nucleus into the egg nucleus. I have not, however, suc- 

 ceeded in finding any structural basis for such segmentation. 



Figures 19 and 20 show two sections of another egg in 

 which fertilization has already taken place. Here again 

 (fig. 19) we find the cytoplasmic envelope in the depres- 

 sion in the side of the nucleus. The extent of this depression 

 may be seen by comparing the vertical diameter of the 

 nucleus in figure 19 with the same diameter in figure 20. 

 Although this cytoplasmic part is fainter and less distinct 

 here than in figure 13, it can be followed easily and seems 

 to be attached to the nuclear membrane of the egg at a. 

 Only about a coil and a half of the sperm-nucleus can be seen 

 here, but it still retains clearly its spiral character. Figures 

 23, 24 and 25 are successive sections of another egg^ In 

 figure 25 the cytoplasmic remnant can be seen in the cyto- 

 plasm outside the nucleus. In figure 24 two pieces of 

 nuclear material are seen, one of which closely envelops a 

 large nucleolus. The same occurs in figures 18 and 19, where 

 the nucleolus n is inclosed by the turn formed by the union 

 of a, figure 18, and 6, figure 17. In figure 23 a large coil of 

 the sperm-nucleus lies in the plane of the section. The disor- 

 ganization of the spermatozoid has become quite marked here, 

 especially in the portion c where it is reduced to a mass of 

 granules showing few of the characters of the spiral nucleus 

 as it enters. 



As a matter of precaution against mistakes the eggs shown 

 in figures 13, 17 and 18, and 23, 24 and 25, have been recon- 



