GROWTH AND DIFFERENTIATION- OF THE GERM-CELLS 



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This tallies with Strasburger's earlier conclusion that the cilia-bearing 

 region consists of " kinoplasm " and corresponds to the middle-piece 

 ('92, p. 139), but gives a still more definite basis of comparison. ^ 



The history of the centrosomc-like hod:\^?. {hlcpharoplasts of Web- 

 ber, '97, 3) has been carefully followed out in Zcwiia and Giugko by 

 Webber ('97), and in Cycas by Ikeno ('97, '98) with nearly similar 

 results. In all these forms (Fig. Zj) the blepharoplasts appear in the 





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.#. 





'rj!iir^- 



r'' 



Fig. 87. — Formation of the spermatozoids in the cycads. \^A, GlNUKO; B-D, /.itm.i 

 Webber; E-I, Cycas, iKENO.] 



A. Developing pollen-tube, showing stalk-cell {s), vegetative cell {v) and generative cell (^). 

 the latter with two blepharoplasts. B. Generative cell, somewhat later, with blepharoplasts and 

 asters. C. The same in the prophases of division, showing breaking up of blepliaroplasts. 

 D. The two spermatids formed by division of the generative cell ; blepharoplasts fragmented ; 

 from these fragments arises the cilia-bearing band. E. Blepharoplast of Cycas, at a stage some- 

 what later than Fig. C; cilia developing. F. Later stage; ciliated band (derived from tlie last 

 stage) attached to a prolongation from the nucleus. G. Cilia-bearing band continuous. //. Nearly 

 ripe spermatozoid with nucleus in the centre; ciliated band, sliown in section, forming a spiral. 

 /. Slightly later stage, viewed from above, showing the spiral course of the band (cilia omitted). 



penultimate cell-generation lying one on cither side the nucleus, and 

 in earlier stages surrounded by a.stral radiations very closely resem- 

 bUng those of a typical mitotic aster, and they lie opposite the poles 



1 The "anterior" region of the spermatozoid thus corresponds to the "posterior" region 

 of the spermatozoon, the confusion of terms having arisen from the fact that the former 

 svi^ims with the ciUa-bearing region in front, the latter with the flagellum directed backward. 



