THE CENTROSOME AND THE BLEPHAROPLAST 



93 



In 1897 and 1901 Webber described the blcpharoplast of Zamia (Fig. 

 33). Up to the time of the division of the body cell the two blepharo- 

 plasts, which arise de novo in the cytoplasm, are surrounded by radiations, 

 but they have no part in the formation of the spindle, which is entirely 

 intranuclear. During mitosis they lie opposite the poles, increase greatly 

 in size, become vacuolate, and break up to many granules : these in the 

 spermatid coalesce to form a spirally coiled cilia-bearign band lying just 

 inside the cell membrane. In his full account (1901) Webber gives an 

 extensive discussion of the homology of the blepharoplast. 



FIG. 33. Spermatogenesis in Zamia. 



A-E, five stages in the vacuolation and fragmentation of the blepharoplast during the 

 mitosis differentiating the spermatids. F, the two spermatozoids in the end of the pollen 

 tube; prothallial and stalk cells below. Compare Fig. 34. A-D, X 350; E, X 1200. 

 (After Webber, 1901.) 



In Ikeno's (1898) account of gametogenesis and fertilization in Cycas 

 it was shown that the blepharoplasts appear in the body cell, lie opposite 

 the spindle poles during mitosis, and break up to granules which fuse to 

 form the spiral band in a manner similar to that described by Webber for 

 Zamia. The behavior of the blepharoplast in Microcycas (Caldwell 

 1907) is essentially the same. 



Chamberlain (1909) observed in the cytoplasm of the body cell of 

 Dioon (Fig. 34) a number of very minute "black granules" which he was 

 inclined to believe originate within the nucleus. Very soon two undoubted 

 blepharoplasts are present, and are apparently formed by the 



