THE CENTROSOME AND THE BLEPHAROPLAST 



85 



is inserted on a "basal granule" (centrosome?) very near the "blepharo- 

 plast" (kinetonucleus?). At the time of cell-division the trophic nucleus, 

 blepharoplast, and basal granule all divide, the division of the blepharo- 

 plast showing certain features suggesting mitosis. Although earlier 

 investigators thought the flagellum also split, the above named workers 

 find that the old flagellum remains attached to one of the daughter basal 

 granules while a new flagellum grows out from the other daughter granule. 



In flagellate organisms, therefore, the centrosome and the blepharo- 

 plast clearly stand in very intimate relationship with one another: in 

 some of the forms they are one and the same organ. 



Thallophytes. Among the earliest investigations of the blepharoplast 

 in algae were those of Strasburger (1892, 1900). During the development 

 of the zoospores of (Edogonium, Cladophora, and Vaucheria Strasburger 





FIG. 26. Blepharoplasts in Thallophytes. 



A-D, formation of the cilia-bearing ring in the zoospore of Derbesia. (After Davis, 

 1908.) E, Stemonitis flaccida: cilia growing from centrosomes during late stage of division 

 in the formation of swarmers. (After Jahn, 1904.) 



found that the nucleus approaches the plasma membrane, which at that 

 point forms a lens-shaped thickening. From this structure grow out the 

 cilia, and at the base of each a small refractive granule is present. The 

 blepharoplasts of the higher groups were believed by Strasburger to have 

 been derived from such swollen ectoplasmic organs of the algae, and that 

 all of them are morphologically distinct from centrosomes. Dangeard 

 (1898) likewise found a deeply staining granule at the base of the cilia 

 in Chlorogonium. 



In Hydrodictyon (Timberlake 1902) the cilia are inserted on a small 

 body lying in contact with the plasma membrane and joined with the 

 nucleus by a delicate protoplasmic strand. The possible relationship 

 of this body with the granules seen occupying the spindle poles during 

 the formation of the spore cells was not determined. In the young 



