296 Trans. Acad. Sci. of St. Louis. 



part, at least, directed backward and exceed in length the body 

 of the spermatozoid, instead of being comparatively short and 

 directed outward as they have previously been described and 

 figured. Their motion passes backward in waves from their 

 origin at the anterior end of the body toward their free ends, 

 so that as much as two waves of motion can sometimes be 

 seen at once following the curves of the body of the sperma- 

 tozoid backward. The cytoplasmic coils and at least the first 

 turn of the nucleus seem to be actively motile also, so that 

 in addition to the whirling motion imparted by the cilia the 

 spermatozoid undergoes a rapid succession of changes of 

 form. I have not determined just how much power of move- 

 ment may be attributed to the nucleus itself, but the fact that 

 the nuclear portion of the spermatozoid enters the egg with- 

 out assistance from the cytoplasm proves that it has that 

 power in some considerable degree at least. 



The Egg-Cell. 



The egg-cell lies in the venter of the archegonium closely 

 invested by the richly nourished cells lining the cavity in 

 which it lies. It varies in diameter from about twenty-five 

 microns to forty microns according to the direction in which 

 it is measured. Its form in different archegonia varies from 

 nearly spherical almost to lens-shaped. The ventral canal- 

 cell lies in a concavity of its upper outer surface but usually 

 not in the center and often very nearly at one side. The dia- 

 gram (fig. 43) is a part of a vertical longitudinal section of 

 a prothallium through the neck of the archegonium and the 

 middle of the egg-cell. Here it is readily seen that the ven- 

 tral canal-cell (v. c. c. ) lies at the bottom of the open neck 

 of the archegonium (N) but that this point lies at one side of 

 the center of the oosphere or egg. The egg extends outward 

 beyond the ventral canal-cell, so that it has come to lie in 

 the side of the egg and to be surrounded by it except on the 

 side turned toward the open neck. Now a section cut in a 

 plane parallel with the line A-B and perpendicular to the 

 plane of the section in figure 43 will explain such appear- 

 ances as the open cavity v which appears in figures 10 and 11 

 and in the diagrams 46, 47 and 48, which are camera outlines 



