190 4.] ON THE CENTROSOME OF HEEATIOEM. 99 



one. The structure of the cells and the process of division are practically 

 the same throughout the whole cell-gmerations. The nucleus contains in 

 its centre a granular mass of chromatic substance and does not seem to 

 have any nucleolus-like body. When the nuclear division is about to take 

 place the nucleus which is usually spherical elongates and assumes a more 

 or less elliptical shape. At each pole of the nucleus there appears a 

 cytoptasmic radiation. Each radiating structure or aster seems to centre 

 to a point just outside of the nuclear membrane almost in close contact 

 with the latter. Here in the centre of the radiation a minute dot which 

 might be taken for a Centrosome has sometimes been observed. But it is 

 not at all a distinct or constant structure and I am not inclined to give 

 any importance to it. When the spindle is formed the aster entirely 

 disappear, and one also fails to see in the spindle pole any structure which 

 might be taken for a Centrosome. Either in the resting stage or in any 

 other stages of the dividing nucleus of the young antheridium I failed to 

 see the structure corresponding to the Centrosome of Ikeno. Only in the 

 last division of the antheridium I found two deeply staining bodies at the 

 spindle poles as figured by Ikeno. Although I have not studied the further 

 behaviour of this body in the development of the spennatozoid, there would 

 be little doubt that it will take part in the formation of cilia as Ikeno 

 described, and may properly be called a blepharoplast. 



I obtained a similar result in the study of FegateJa cornea. The 

 antheridial cells of this plant are larger than those of Marchantia and 

 therefore are more favourable for the study. In the resting nucleus of the 

 antheridial cells, instead of a granular mass of chromatic substance as seen 

 in Marchantia, one large nucleolus was observed. The nucleolus has a dia- 

 meter nearly \ of that of the nucleus, and very little chromatic substance 

 is found in the nuclear reticulum. The nucleolus would probably contribute 

 a considerable part of its substance to the formation of chromosomes. 



The antheridial cells of Pellia, Aneura and Malrinoa are considerably 

 larger compared with those of Marchantiaceoe. The nulear division in the 

 antheridium of these three genera agrees in its essential points. The 

 nucleus contains a nucleolus which is of ordinary size. Just before the 

 nucleus divides, it assumes more or less elliptical shape and two cytoplas- 

 mic radiations or asters are seen at opposite poles of the nucleus. In the 

 centre of the radiating structure I failed to recognize any distinct body 

 which corresponds to the Centrosome. With the formation of the spindle, 

 asters gradually disappear and at the poles of complete spindle one fails to 



