THE CENTROSOME AND THE BLEPHAROPLAST 97 



apparatus as entirely independent of centrosomes, holding rather that it 

 is produced by the differentiation of chondriosomes, and that the resem- 

 blance of ciliated cells to spermatids, in which centrosomes do produce 

 the motor apparatus, is an accidental one. 



Conclusion. In conclusion it may be said that it is highly probable 

 that cilia-bearing structures are not homologous in all plant and animal 

 groups. It is beyond question that in animals the centrosomes of the 

 spermatid produce the motor apparatus of the spermatozoon. That a 

 similar interpretation is to be placed upon the blepharoplasts in the sper- 

 matids (androcytes) of bryophytes, pteridophytes, and gymnosperms 

 appears to be equally well demonstrated. The blepharoplasts of the 

 flagellates are also probably centrosomic in nature, at least in certain 

 cases. In the " plasmodermal blepharoplasts" of motile alga cells we 

 have organs which, in the light of our present knowledge, do not appear 

 to belong to the centrosomic category, but final disposition of them must 

 await further information concerning those algae which possess both cen- 

 trosomes and blepharoplasts. It can scarcely be doubted that the basal 

 corpuscles of ciliated cells represent organs belonging to various categories. 

 It must be left for further research to determine just how far these 

 structures, which are functionally analogous, are homologous with each 

 other and with other cell organs. 



Bibliography 5 



Centrosome and Blepharoplast 



ALLEN, C. E. 1912. Cell structure, growth and division in the antheridia of Poly- 



irichum juniperinum Willd. Arch. Zellforsch. 8: 121-188. pis. 6-9. 

 1917. The spermatogenesis of Polylrichum juniperinum. Ann. Bot. 31: 269-292. 



pis. 15, 16. 

 ALLEN, R. F. 1911. Studies in spermatogenesis and apogamy in ferns. Trans. Wis. 



Acad. Sci. 17: 1-56. pis. 1-6. 

 BELAJEFF, W. 1888. Ueber Bau and Entwicklung der Spermatozoiden der Gefass- 



kryptogamen. Ber. Deu. Bot. Gesell. 7: 122-125. 

 1894. Ueber Bau und Entwicklung der Spermatozoiden der Pflanzen. Flora 79 : 



Erganzb.: 1-48. pi. 1. 

 1897a. Ueber den Nebenkern in spermatogenen Zellen und die Spermatogenese 



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1898. Ueber die Cilienbildner in spermatogenen Zellen. Ibid. 16: 140-144. pi. 7. 



1899. Ueber die Centrosome in den spermatogenen Zellen. Ibid. 17: 199-205. 

 pi. 15. 



VAN BENEDEN, E. 1876. Recherches sur les Dicyemides, survivants actuelles d'un 

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1883. Recherches sur la maturation de 1'oeuf, la fecondation et la division cellu- 

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