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nucleus into the cytoplasm and divided itself into two parts, which 

 during mitosis wandered to the poles of the spindle, like true centro- 

 somes. Since then these centrosomes have been found again in many 

 other liverworts, hut according to some observers, they seem to be 

 absent from the divisions in the antheridia of Pellia. 



At the diaster stage the centrosome disappeared, only to emerge 

 again from the nucleus at a subsequent division. At the last division 

 only of the antheridial cells it remained in the cytoplasm and was 

 transformed into the hlepharoplast. For this reason Ikeno considers 

 the hlepharoplast of the liverworts to be homologous with the 

 centrosome. 



Many arguments, both for and against this view, have afterwards 

 been advanced, which we will not discuss further. Without a detailed 

 review of the literature such a discussion would scarcely be possible. 



Our results with Polytrichum agree in part with those published 

 by Ikeno and others, but also at the same time differ from them in 

 certain respects. 



I. On t/w growth of tin' antheridial cells mid mi spermatogenesis. 



In the antheridia the cells are closely packed. The nuclei are 

 spherical and contain at their centre a substance, which is deeply 

 stained by iron-haematoxylin. We do not propose to discuss whether 

 this is, or is not, a nucleolus. There is no agreement in the literature 

 on this point and different investigators designate by nucleolus the 

 most widely different structures. It is, however, usual in botanical 

 literature to call such a body a nucleolus, though it also takes up 

 the other chromatin stains very readily. However this may be, the 

 dark mass lies in the middle of the nucleus, and slightly more to- 

 wards the periphery there is, in addition, another fairly large, black 

 corpuscle. 



If nuclei are examined in various stages of rest and mitosis, those, 

 which are furthest removed from their next division only show the 

 central black mass. A little later the corpuscle also appeal's, at first 

 connected to the central mass by a thin black thread. Soon this 

 connexion disappears and the corpuscle approaches more and more 

 the nuclear membrane. After some time it emerges from the nucleus 

 and remains imbedded in the cytoplasm, in contact with the nuclear 

 membrane. The corpuscle which was at first round, now becomes 

 rod-shaped and afterwards undergoes constriction in the middle, thus 

 assuming a dumb-bell shape. It subsequently divides into small spheres, 

 which move along the nuclear membrane and which become more 



