Thorn — Ftrtilization in Aspidium and Adiantum. 311 



are characteristic of spermatogenesis. Fusion is there a 

 union of entire nuclei. The generative nucleus is carried 

 in the end of the pollen-tube until in contact with the egg or 

 nearly so. Similarly in the fern the entire nucleus is carried 

 in its cytoplasmic envelope until it is actually within the cyto- 

 plasm of the egg cell. 



Summary of Results. 



1. As the spermatozoid enters the mouth of the archego- 

 nium it consists of a proximal (with reference to the egg) 

 cytoplasmic portion of about one and a half coils and a distal 

 nuclear portion of about two spiral coils. 



2. The cytoplasmic forward end contains or is partially 

 derived from the so-called ** blepharoplast " and bears numer- 

 ous long cilia. This part either becomes disconnected en- 

 tirely before the spermatozoid reaches the egg, or, becoming 

 functionless, is turned backward and dragged passively along 

 into the cytoplasm of the egg, 



3. The sperm-nucleus consists of an outer homogeneous 

 appearing chromatin mass and an inner ** ground substance '* 

 derived apparently from the nucleoli of the spermatid. The 

 whole body is surrounded by a cytoplasmic envelope. 



4. The nucleus once inside the archegonium displays the 

 power of motion toward and into the egg independently of 

 its ciliate anterior end, which indicates that the attractive 

 impulse which leads to fertilization is exerted directly between 

 the nuclei. 



5. The egg has a concave depression in its outer surface 

 in which the spermatozoid is found coiled before fertilization. 



6. The egg nucleus has an irregular branching form extend- 

 ing through the cytoplasm in all directions. It contains one 

 or more prominent nucleoli and a network bearing extremely 

 minute chromatin granules. It has on its outer surface a 

 concavity similar to and nearly parallel with the concavity in 

 the surface of the cell, and approaches most nearly to the 

 surface at this point. 



7. The nuclear coils of the spermatozoid lying in the con- 

 cavity of the egg break their way into the cytoplasm of the 



