1899] ANTHEROZOIDS IN GYMNO SPERMS 271 



A similar occurrence has been recorded by Strasburger (Histol. Beitr. 

 Heft iv.) in certain Coniferae, but in this case the division is parallel 

 to the axis of the pollen tube, and a distinct wall is formed. With this 

 difference, however, the processes are identical, and the crushed nucleus 

 of Cycads must be looked upon as homologous with Strasburger's " stalk " 

 cell, while its sister nucleus corresponds to that of his " body " cell. 



At this stage the embryonal nucleus begins to move back from 

 the apex of the pollen tube, and eventually comes in contact with the 

 body cell, now considerably enlarged, elliptical in outline, and filled 

 with dense protoplasm. The exine covered remains of the pollen 

 grain thus contain, besides the body cell, the outer germinal cell, the 

 nucleus of the embryonal cell, and that of the stalk cell, all of which 

 presently swell up and disappear, being apparently absorbed by the 

 body cell, which continues to increase in size and eventually divides, 

 the daughter cells remaining for some time connected by a strand of 

 faintly staining cytoplasm. The plano-convex cells which result from 

 this division lie with their flat surfaces in contact, and become the 

 antherozoids. Each consists of a large nucleus enveloped in a com- 

 paratively thin sheath of cytoplasm, in which not far from the centre 

 of the convex side there appears a short band, the origin of which is 

 tentatively ascribed by the author to the centrosome. This band, at 

 first composed of granules which soon fuse to form a filament, comes 

 in contact with a beak-like process thrown out by the nucleus, increases 

 rapidly in length, and finally describes four or five complete spiral 

 convolutions directly beneath the convex surface of the antherozoid. 

 Its outer face is clothed with cilia, which, formed at first within the 

 cell, ultimately project beyond it into a spiral groove running parallel 

 to the band, and indenting alike cytoplasm and nucleus. The anthero- 

 zoids when ripe escape from the pollen tube into the fluid-filled space 

 within the membranous remains of the nucellus ; here they swim to 

 the neck of the archegonium and thus enter the egg cell, where the 

 nucleus slips out of its cytoplasmic sheath, leaving it to disappear in 

 the upper part of the cell while it moves down to the centre to fuse 

 with the nucleus of the egg. 



The Broad Path. 



Every one has no doubt heard of the ingenuous youth who defined 

 Grimm's Law as the law whereby any consonant could be replaced by any 

 other, but we have sometimes wondered whether a definition of biology 

 on similar lines might not prove acceptable to some of its students. 

 As thus — Biology is the science which proves that everything is in 

 process of being converted into something else, and that tin's has an 

 important bearing on human life. We recommend the definition to the 

 notice of the versatile author of " Cycling : its Effect on the Future of 



