86 



INTRODUCTION TO CYTOLOGY 



zoospore cell of Derbesia (Davis 1908) the nucleus migrates toward the 

 plasma membrane, and from it many granules, which are not centrosomes, 

 move out along radiating strands of cytoplasm to the surface of the cell, 

 where by fusion they form a ring-shaped structure from which the cilia 

 develop (Fig. 26, A-D). In the developing spermatozoid of Chara 

 (Belajeff 1894; Mottier 1904) the blepharoplast arises as a differentiation 

 of the plasma membrane and bears two cilia. No centrosomes or other 

 granules were seen at the base of the cilia, although Schottlander (1893) 

 had previously reported centrosomes in the cells of the spermatogenous 

 filament. 



In the zoospore of the fungus Rhodochytrium (Griggs 1904) there is a 

 deeply staining body at the insertion point of the cilia; this is connected 

 by fine cytoplasmic fibers with the nucleus. In the myxomycete Stemo- 

 nitis Jahn (1904) made an observation that is highly suggestive in con- 

 nection with the question of the relationship of the centrosome and the 

 blepharoplast. At the last mitosis in the formation of the swarmers the 

 spindle poles are occupied by centrosomes, and during the anaphases 

 the flagella of the resulting swarmers grow out directly from these cen- 

 trosomes (Fig. 26, E), just as in the spermatocytes of certain insects 

 (p. 95). 





W^m 



'.L-l-^J 



Fig. 27. — Spermatogenesis in Marchantia. 



b, blepharoplast; c, centrosome; c.n., " chromatoider Nebenkorper ; " n, nucleus. 



I After Ikeno, 1903.) 



Bryophytes. — Among the bryophytes the blepharoplasts of Mar- 

 chantia and Fegatella (Conocephalus) have received much attention. 

 According to Ikeno (1903) a centrosome comes out of the nucleus at 

 each spermatogenous division in Marchantia and divides to form two 

 which separate to opposite sides of the cell, occupy the spindle poles, 

 and disappear at the close of mitosis: it is possible that they are included 

 in the daughter nuclei. After the last (diagonal) division, however, they 

 remain in the cytoplasm as the blepharoplasts, elongating and bearing- 

 two cilia (Fig. 27). Another body, the chromatoider Nebenkorper, is 



