DIVISION OF COLLAR-CELLS OP CLATHRINA CORIACEA. 611 



The Division of the Collar-Cells of Clathrina 

 coriacea (Montagu): A Contribution to the 

 Theory of the Centrosome and Blepharo- 

 plast. 



By 



ITIiiriel ICobei'tsoii, i?I.A., aucl £. A. Miiicliin, M.A. 



With Plates 25 and 26. 



Introductory. 



-^ At the present time there is a great deal of confusion in the 

 use of the words " blepharoplast " and " centrosome." Two 

 distinct questions arise with regard to the significance of these 

 bodies; the first is the question of the homology of blepharo- 

 plasts and centrosomes; the second is that of the nature of the 

 centrosome, and more particularly whether or not it is to be 

 regarded as equivalent primarily to a nucleus. 



With regard to the first of these questions, it is now 

 generally admitted that blepharoplasts and centrosomes are 

 essentially bodies of the same nature, for reasons that will 

 presently be considered at greater length. The difference 

 between a centrosome and a blepharoplast, on this view, is 

 entirely a matter of divergence of function. A centrosome 

 may be briefly characterised, in a general way, as a body 

 which exerts or governs kinetic functions in relation to the 

 division of the nucleus; a blepharoplast may be defined as 

 a centrosome which governs the movements of motile 

 organs, such as flagella, which arise from it and are in 

 direct or indirect connection with it. 



With regard to the second of these questions^ namely, the 

 nature of the centrosome, two opposite views are current, 



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