GROWril AND DIFFERENTIATION OF THE GERM-CELIS 



173 



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 centrosome-like bodies {blcpharoplasts of Web- 

 ber, '97, 3) has been carefully followed out in Zamia and Gingko by 

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

 results. In all these forms (Fig. "^j) the blcpharoplasts appear in the 



G H 



Fig. 87. — Formation of the spermatozoids in the cycads. [.-/, GiNGKO; B-D, Zamia, 

 Webber; E-I, Cycas, iKENO.] 



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

 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 blepharoplasts. 

 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 the last 

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

 ripe spermatozoid with nucleus in the centre; ciliated band, shown 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 either side the nucleus, and 

 in earlier stages surrounded by astral radiations very closely resem- 

 bling 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 

 •swims with the cilia-bearing region in front, the latter with the flagellum directed backward. 



