PTERIDOPHYTA. 



'35 



Belajeff ('99), who has also studied the development of the sperma- 

 tozoid in Marsilia, agrees with Shaw in so far as the transformation 

 of the primordium of the blepharoplast into the mature cilia-bearing 

 organ is concerned, but, as regards the earlier behavior of the primordia, 

 these observers disagree in certain important particulars. Belajeff, 

 who regards the blepharoplast as a centrosome, finds that in the 

 division of the grandmother-cell of the spermatozoid, the primordia, 

 which lie some distance from the nucleus, divide, and a faint central 

 spindle is formed between the daughter primordia. This structure, he 

 maintains, gives rise to the karyokinetic spindle just as in some animal 



II 



G 



FIG. 54. Transformation of mother-cell into matare spermatozoid in 

 Marsilia vestita.. (After Shaw.) 



E, two spermatozoid mother-cells ; each rudiment of blepharoplast has 



become a group of granules. 



F, spermatozoid mother-cell ; the blepharoplast (b) is much elongated. 



c , cytoplasm ; s, starch grains. 



G, the thread-like blepharoplast and bean-shaped nucleus lie close to 

 plasma membrane. 



H, an older stage seen from above; it is apparent that blepharoplast is a 



band concave on the outside. 

 I, the blepharoplast and sausage-shaped nucleus (k) make several spiral 



turns within the cell close to plasma membrane. 



cells, and concludes, therefore, that the blepharoplast primordia are 

 centrosomes. The author has already dealt with this matter in the 

 introductory chapter, and a further discussion will not be given here. 



In Equisetum Belajeff has found that the spermatozoid develops in 

 a manner similar to that of the fern, and there are good reasons for 

 believing that the process of development is much the same in the 

 majority of archegoniates, although our knowledge is yet too meager 

 to warrant any sweeping generalization. 



It seems fitting in this connection to compare the mature spermato- 

 zoid of the Characece with that of the fern. Belajeff ('94) has shown 

 that in the development of the spermatozoid of Charafcetida the two 

 cilia are borne by a thread-like body which arises in the cytoplasm in 

 a manner similar to the blepharoplast of the fern. The spermatozoid, 



