172 THE GERM- CELLS 



It is an important question whether the axial filament actually 

 arises from the substance of the centrosome or is formed by differ- 

 entiation from the cytoplasmic substance, after the fashion of an 

 astral ray or spindle-fibre. Meves ('97, p. 117) accepts the latter 

 alternative ; but the observations of Korff on Helix and of Suzuki 

 on elasmobranchs seem to show clearly that, in these cases at least, 

 the inner centrosome elongates bodily to form an extremely long fila- 

 ment traversing the greater part of the flagellum, and apparently of 

 the same nature as the true axial filament developed from the outer 

 or distal centrosome. This seems to establish a probability in favour 

 of the first of the above alternatives, and to show that contractile 

 elements may be directly derived from the centrosome-substance. 

 If this be true, this substance is itself nearly related with " archo- 

 plasm " ; and the origin of a centrosome de novo may be brought 

 under the same category with the formation of archoplasm. 1 



3. Formation of the Spermatozoids in Plants 



While the origin of the spermatozoids has not yet been as fully 

 investigated as that of the spermatozoa, recent researches have given 

 good ground for the conclusion that essentially similar phenomena 

 are involved in the two cases. All recent observers are agreed that 

 the nucleus of the spermatozoid is directly derived from that of the 

 spermatid, while the cytoplasm of the latter gives rise to the cilia and 

 to certain other structures. The principal interest of the subject now 

 lies in the origin of the cilia and their relation to the " archoplasmic " 

 or "kinoplasmic " structures of the mother-cell. Belajeff ('92, '94) 

 found that in Cham the cilia grow forth from a small, highly refract- 

 ing body, taking an intense plasma-stain, that lies in the cytoplasma 

 beside the nucleus. He afterward found the same body " which 

 reminds one of a centrosome" in the developing spermatozoids of 

 ferns and Equisetaceae (Fig. 88), where it grows out into a band, 

 lying in the anterior part of the spermatozoid, from which the cilia 

 grow forth. Comparing these results with those of Hermann, Bela- 

 jeff concluded "that the deeply staining corpuscle" (i.e. the cen- 

 trosome) "in the spermatids of the salamander and the mouse 

 corresponds completely to the deeply staining corpuscle in the sper- 

 matogenic cells of the Characeae, ferns, and Equisetaceae " ; that, 

 furthermore, " the middle-piece of the spermatozoon represents the 

 band which bears the cilia of the plant spermatozoid, while the tail- 

 like flagella 2 of the salamander or mouse represents the cilia." 3 



1 Cf- P- 3 21 - For the function of the centrosome in fertilization, see p. 208. 



2 In the original " Fa'den " perhaps meant to designate the axial filament. 

 8 '97. 3- 



