( 363 ) 



Meanwhile the centrosome has also changed its form. It lias become 

 somewhat longer and more or less cudgel-shaped. At the obtuse end 

 a thin band then becomes visible, which goes along the periphery 

 of the cell. The progressive differentiation of this band starts from 

 the centrosome and proceeds in the direction of the nucleus. The 

 latter has also travelled to the periphery, at that side, which is 

 opposite the centrosome. 



A similar band, which extends from the blepharoplast to the 

 nucleus, has also been described by Ikeno. According to him it 

 originates in the cytoplasm and is .-tamed in the same way as the 

 latter, but more intensely. 



In our preparations which were -tamed with iron-haematoxylin, 

 ii i- very clearly visible and sharply marked out in black, but a 

 difference from the staining of the chromatin may nevertheless lie 

 observed. 



While this band slowly grows out and the "chromatoïde Neben- 

 körper" disappears, a quantity of chromatin is separated oil' for the 

 third time from the chromatin mass of the nucleus. This time however, 

 only a very .-mall body is formed, which also emerges from the 

 nucleus, but mostly remains very close to the nuclear membrane ; 

 the latter can only be seen very indistinctly. 



In a somewhat later stage the band extends along half the circum- 

 ference of the cell and has therefore nearly reached the nucleus. 

 The third chromatin body is found at the end of the baud and in 

 contact with the nucleus, so that in the spermatozoid it lies between 

 the band and the modified nucleus. 



The changes which the nucleus itself undergoes in the formation 

 of the spermatozoid have already been described in detail by Stras- 

 birger and others ; it seems to us therefore unnecessary to investi- 

 gate this matter further. 



II. Development of the Ovum and Fertilisation. 



In the young archegonia the mother cell of the ovum is especially 

 large. During the further development of the archegoniuin this cell 

 divides into two and thus gives rise to an ovum and a ventral 

 canal-cell. A point of difference from many other mosses is, that in 

 the species of Polytriehum, which we have examined, the two 

 cells are of exactly the same size. These cells now round themselves 

 off and then lie loose in the venter of the archegonium. The venter 

 increases in size and the cells which have been rounded off, separate 

 from each other, till one lies at the base of the venter, and the 



24 



Proceedings Royal Acad. Amsterdam. Vol. X. 



