Thorn — Fertilization in Aspidium and Adiantum. 303 



the section as a hole in the egg-cytophism opening to the 

 outside beneath the plane of the section. Here a blunt end of 

 the spermatozoid is seen extending through the cytoplasm, 

 interrupting or breaking the nuclear membrane and actually 

 entering the nucleus itself. The contour of the nucleus is 

 drawn at the plane where the nuclear membrane is interrupted 

 for the entrance of the spermatozoid. The appearance of 

 this nucleus is fairly typical for a vertical longitudinal section 

 at this stage. If the section were above the plane of this 

 section, the nucleus would show a contour much more nearly 

 round. We have here a figure where the nuclear portion of 

 the spermatozoid lies partly inside the nucleus of the egg, a 

 pari extends through the cytoplasm and a portion still lies 

 coiled in a depression in the surface of but entirely outside 

 the egg. That is, the actual process of the union of the two 

 gametes is before us. 



In figure 11 we have a similar condition. The nucleus in 

 this section lies very close to the surface of the cell — 

 the bottom of the depression in its surface v. Only a 

 small portion of the spermatozoid remains in this case — the 

 larger part was carried away by the knife and will be found 

 in the next section. Here again the portion present lies 

 partly inside and partly outside the egg nucleus and it enters 

 blunt end first. In figure 12 the Qgg cell had no depression 

 in its upper surface. The spermatozoid has broken through 

 the very tip of the cell. The part present shows the dis- 

 tinctly spiral appearance of the spermatozoid and is certainly 

 enterino; large end first. 



We get a more striking condition in figure 13 than in any 

 of the others. Here one large coil and a half smaller, a, are 

 seen lying outside the point b where the spermatozoid breaks 

 through the nuclear membrane. The entire nuclear portion 

 (stained deeply) lies inside the Qgg nucleus but is connected 

 distinctly or rather is continuous with the coils lying outside 

 the nucleus. In this figure the Qgg nucleus is drawn in the 

 plane where the spermatozoid breaks through the nuclear 

 membrane. The lightly colored coils of the spermatozoid 

 contain no nuclear material. The part from a to b lies in the 

 concave depression of the nucleus which is just below the 



