THE CENTROSOME AND THE BLEPHAROPLAST 95 



sustain the homologies suggested by BelajefT. Be pointed oul thai in 

 Marchantia centrosomes are present in all the spermatogenoua divisions, 

 whereas in other liverworts they appear much later, and from this he 

 argued that the bryophytes show various stages in the elimination of the 



centrosome. He strongly reasserted his belief thai blepharoplasts are 

 centrosomes, and spoke of the "transformation <>f ;i centrosome into a 

 blepharoplast" in the development of a spermatid into a spermatozoid. 

 The ectoplasmic blepharoplasts of the algae were also held to be derived 

 from centrosomes. In the second paper he insisted less si rongly upon t he 

 morphological identity of all blepharoplasts, separating them into three 

 categories: (1) centrosomatic blepharoplasts, including those of the myxo- 

 mycetes, bryophytes, pteridophytes, and gymnosperms; (2) plasmoder- 

 mal blepharoplasts, including those of Cham and some Chlorophyceae; 

 (3) nuclear blepharoplasts, found only in a few flagellate-. 



For a further discussion of this question the student is referred to 

 the present author's papers on Equisetum and Marsilia. The main 

 conclusions reached may be stated in t wo extract s from the former paper: 



Although limited to a single mitosis in the antheridium, the blepharoplasl 

 fof Equisetum] retains in its activities the most unmistakable evidence- of a 

 centrosome nature, and at the same time shows a metamorphosis strikingly like 

 that in the cycads. In thus combining the main characteristics of true centro- 

 somes with the peculiar features of the most advanced blepharoplasts, it reveals 

 in its ntogen3 r an outline of the phylogeny of the blepharoplast as it i> Been 

 developing through bryophytes, pteridophytes, and gymnosperms, from a func- 

 tional centrosome to a highly differentiated cilia-bearing organ with very lew 

 centrosome resemblances. 



The activities of the blepharoplast in Equisetum [Marsilia, and Blasia], 

 taken together with the behavior of recognized true centrosomes in plants ami 

 analogous } henomena in •animals, are believed to constitute conclusive evidence 

 in favor of the theory that the blepharoplasts of bryophytes, pteridophytes, and 

 gymnosperms are derived ontogenetically or phylogenetically from centre-.. me-. 



Animals. — The early researches of Moore (1895), Meves I L897, L899 . 

 Korff (1899), Paulmier (1899), and many other more recent investigators 

 have established 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 tail growing oul 

 directly from it (Fig. 35). Henneguy (1898) even saw flagella attached 

 to the centrosomes of the mitotic figure in the spermatocyte of an insect. 

 an observation which has been often repeated. Wilson L900, p. 17.'. 

 concludes that "the facts give the strongest ground for the conclusion 

 that the formation of the spermatozoids agrees in its essential featuri 

 with that of the spermatozoa . . . and that the blepharoplasl is 

 without doubt to be identified with the centrosome. 



