igi2] SHARP— SPERMATOGENESIS IN EQUISETUM III 



Through his work on Marchantia Ikeno was led to state a view 

 which might appear to lessen the contrast between the above two 

 theories. He pointed out (54) the resemblance between the elonga- 



tion of the blepharoplast along the plasma membrane of the 

 Marchantia spermatid and the formation of the thickened portion 

 of the Hautschicht in the algae as described by Strasburger and 

 others, and concluded that this thickening has almost without doubt 

 been derived from a centrosome ontogenetically or phylogenetically, 

 that it is the metamorphosis product of a centrosome. His belief 

 that the basal body in the swarm spore of Hydrodictyon is to be 

 accounted for in a similar way was strengthened by the fact that 

 Timberlake (85) observed what were evidently centrosomes at 

 the poles of the spindles giving rise to the spore Anlage. In his 

 later paper (55) Ikeno is less inclined to include the algal Haut- 

 schicht organs in the same morphological category with the blepharo- 

 plasts of the higher plants, but places them in a class apart — "plas- 

 modermal blepharoplast s." 



In the light of our limited knowledge of the history of the bleph- 

 aroplasts in algae it seems wisest to make this disposition of them 

 for the present. Otherwise we should be compelled to assume 

 their homology with those of the higher groups from which they 

 differ so widely in origin, appearance, and general behavior. Since 

 we can no longer remain in doubt concerning the centrosome nature 

 of the blepharoplast of higher plants, this assumption would mean 

 that the alga blepharoplast has lost all centrosome properties and 

 now arises in the motile cell itself in a very modified manner, making 

 it farther advanced in this respect than those of the higher groups^ 

 which we can hardly regard as probable. Before any final judg- 

 ment can be rendered on this question more data must be gathered 

 from the algae themselves, from those forms which show both cen- 

 trosomes and blepharoplasts in their life histories. 



The researches of Moore (68), Meves (63, 64), Korff (58), 

 Patjlmier (72), and several others have established beyond ques- 

 tion the fact that the centrosome (or centrosomes) of the animal 

 spermatid plays an important role in the formation of the motor 

 apparatus of the spermatozoon, the axial filament of the nagellum 



