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INTRODUCTION TO CYTOLOGY 



The results of Shaw were in the main confirmed by the later work of 

 Sharp (1914), who, however, saw in the achromatic structures accom- 

 panying the blepharoplast striking evidence in favor of Belajeff's view 

 of its homology. In line with this conclusion the suggestion has recently 

 been made (Sharp 1920) that the fragmentation of the blepharoplast 

 in Bla.sia, Equisetum, Marsilia, and the cycads may be homologized with 

 the normal division exhibited by ordinary centrosomes. 



Fig. 32. — Spermatogenesis in Marsilia quadrifolia. 

 A, first spermatogenesis mitosis; no centrosomes. B, second mitosis, centrosomes 

 present. C, third mitosis; centrosomes present; old centrosome divided and degenerating 

 in cytoplasm. D, penultimate spermatogenous cell; daughter centrosomes separating. 

 E, last spermatogenous mitosis; blepharoplasts (centrosomes) becoming vacuolate. F, frag- 

 mentation of blepharoplast in spermatid. G, transformation of spermatid into spermato- 

 zoid. H, free swimming spermatozoid. X 1400. {After Sharp, 1914.) 



Gymnosperms. — The first known blepharoplast in plants above the 

 algae was discovered in Ginkgo by Hirase in 1894. He observed two, one 

 on either side of the body cell nucleus, and because of their great simi- 

 larity to certain structures in animal cells he believed them to be attrac- 

 tion spheres. In 1897 Webber observed the same bodies, and noted their 

 cytoplasmic origin. On account of certain differences between these 

 organs and ordinary centrosomes he expressed the opinion that they are 

 not true centrosomes, but distinct organs of spermatogenous cells. 

 The blepharoplast of Ginkgo was later investigated by Fujii (1898, 1899, 

 1900) and Miyake (1906). 



