THE SPERMATOZOON 



107 



to the spermatozoon. The spermatozoids are in general less highly 

 differentiated than spermatozoa, and often show a distinct resemblance 

 to the asexual swarmers or zoospores so common in the lower plants 

 (Figs. 52, 5,3). They differ in two respects from animal spermatozoa; 

 first in possessing not one but two or several flagella ; second, in the 

 fact that these are 

 attached as a rule not 

 to the end of the cell, 

 but on the side. In 

 the lower forms plas- 

 tids are present in 

 the form of chromato- 

 phores, one of which 

 may be differentiated 

 into a red " eye-spot,' 

 as in Volvox and 

 Ft tens (Figs. 41, 53, 

 A), and they may 

 even contain contrac- 

 tile vacuoles (Volvox) ; 

 but both these, struct- 

 ures are wanting in 

 the higher forms. 

 These consist only of 

 a nucleus with a very 

 small amount of cyto- 

 plasm, and have typi- 

 cally a spiral form. 

 In C/iara, where their 

 structure and devel- 

 opment have recently 

 been carefully studied 

 by Belajeff, the sper- 

 matozoids have an 

 elongated spiral form 

 with two long flagella 

 attached near the 

 pointed end which is 

 directed forwards in swimming (Fig. 52). The main body of the 

 spermatozoid is occupied by a dense, apparently homogeneous nu- 

 cleus surrounded by a very delicate layer of cytoplasm. Behind the 

 nucleus lies a granular mass of cytoplasm, forming one end of the 

 cell, while in front is a slender cytoplasmic tip to which the flagella 

 are attached. Nearly similar spermatozoids occur in the liverworts 



Fi S- 53- Spermatozoids of plants. [A, B, C, E, after 

 GUIGNARD; D, F, after STRASBURGER.] 



A. Of an alga (Fucus) ; a red chromatophore at the right 

 of the nucleus. B. Liverwort (Pellta). C. Moss (Sphagnum). 

 D. Marsilia. E. Fern {Angiopteris). F. Fern, Phegopferis (the 

 nucleus dark). 



