THE CENTROSOME AM) THE BLEPHAROPLAST 



v 



is inserted on a "basal granule" (centre-some?) 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 earliei 

 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 





aim 





r '<£> ~ ■■'- <■>- vx -■ 









, 



/ 



*WK3 



\ 



HI 



Fig. 26.— Blepharoplasts in Thallophytes. 



A-D, formation of the cilia-bearing ring in the zoospore of Derbe&ia. {After Davis, 

 1908.) E, Stemonitis flaccida: cilia growing from centrosomes during late stage <>f ili\ i- ; 

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



isior 



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

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

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

 blepharoplasts of the higher groups were believed by Strasburger to hav< 

 been derived from such swollen ectoplasmic organs of the alg«, 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 smal] 

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

 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 



