802 Trans. Acad. Sci. of St. Louis. 



tion in s, figure 4, and we have sufficient grounds for saying 

 that the attractive impulse which leads finally to fertilization 

 must be exerted directly upon the nuclear portion of the sper- 

 matozoid. This portion, as seen in figures 2 and 4 and also in 

 the fertilization figures 10, 11 and 12, must have the same 

 power to respond by motion toward the egg when it lies outside 

 that it undoubtedly has after it is inside the egg cytoplasm. In 

 the fertilization of the animal egg (Wilson, 1896; Wheeler, 

 1896) the tail of the spermatozoid furnishes the motive power 

 until the nucleus enters the cytoplasm of the egg. The tail is 

 left outside, or if carried in is functionless. The nuclear por- 

 tion ofteu traverses many times its own diameter before fusion 

 with the nucleus of the egg. In the fern we have a spiral 

 nucleus in the spermatozoid, at least one turn of which is 

 actively motile. In either case the directive influence must be 

 exerted on the nucleus. The only difference then is that in 

 the fern we are describing, its influence is exerted upon the 

 nucleus alone and responded to a little earlier. The cyto- 

 plasmic portion may be dropped or become functionless as a 

 locomotive organ before the gametes are in actual contact 

 without interrupting or interfering with their ultimate fusion. 



One or more spermatozoids finally come to lie in the de- 

 pression in the upper surface of the egg (figs. 3, 4, 10) 

 where they may be often seen coiled in the sections examined. 

 Others may be found in almost any position upon the surface 

 of the egg cell (figs. 1, 3). One spermatozoid now bores 

 or forces its way into the cytoplasm of the egg (figs. 4, 6) 

 toward the nucleus. In figure 6 there is no depression in 

 the surface and we find the spermatozoid entering the cyto- 

 plasm near the tip of the egg. In figure 4 the depression is 

 not clearly marked as in figure 3, but there is a marked flat- 

 tening and slight concavity of surface. In both of these 

 cases the pointed forward end penetrates first. Although not 

 so marked in these figures as in figures 10, 11 and 12, the 

 spermatozoid usually breaks in toward the center of the con- 

 cavity of the nucleus, which usually lies closest to the surface 

 at the base of the depression in the surface of the cell. 



In figure 10 we see a portion of the spermatozoid/ coiled 

 in the depression in the surface of the egg which appears in 



