Thorn — Fertilization in Aspidium and Adiantum. 801 



neck of an archegoniura which is ripe for fertilization, es- 

 capes again, or even endeavors to escape. 



Entrance into the neck of the archegonium is always 

 effected with the pointed or cytoplasmic end forward. 

 In entering they become usually drawn out into more, but 

 shorter, turns. Figure 2 represents a striking condition. In 

 this figure the two prominent spermatozoids, a and b, are di- 

 rected into the archegonium large end first, while their pointed 

 ends are entangled with those which lie in the outer portion 

 of the neck. These might appear to be cases where the 

 spermatozoids once in are endeavoring to escape. But a 

 comparison with the spermatozoid in the neck of the arche- 

 gonium in figure 4 and with figure 4a, where the spermato- 

 zoid lay just outside the mouth of the archegonium, suggests 

 a different explanation. In figure 4a the cytoplasmic por- 

 tion c is already disconnected and turned backward. In fig- 

 ure 4 the cytoplasmic end c of the spermatozoid s, though 

 not broken off, is turned backward as if useless. A similar 

 portion c' of the spermatozoid y* seen entering the egg seems 

 to be dragged into the cytoplasm backward. The same has 

 also occurred apparently in c", figure 6. Such figures, com- 

 bined with the fertilization figures 9, 10, 11, 12, lead to the 

 conclusion that as soon as the spermatozoid has entered the 

 mouth of the archegonium the function of the anterior end 

 is completed; consequently when it appears in any later 

 stage it is merely passively dragged along. The fact that 

 this portion is at times broken off, at times turned back- 

 ward, and, as Ikeno has shown, entirely dropped before 

 fusion, indicates that it contains nothing essential for fertiliza- 

 tion. It contains the blepharoplast. This would prove that 

 the blepharoplast is not essential to fertilization in the sense 

 in which a centrosome is given that character, but a special 

 organ differentiated for the production of cilia. In figure 2 

 the aggregation of the chromatin toward the ends of a and b 

 which are inside the venter of the archegonium, compared with 

 figures 9, 10, II and 12, is good evidence that each spermato- 

 zoid is endeavoring to get its entire body inside the arche- 

 gonium not to escape. Combine this with the separation of 

 the cytoplasmic end in figure 4a and its marked loss of func- 



