ZOOFLAGELLATES 161 



bodies (which have their fibril attachments on their nuclear faces) 

 are applied closely against the nuclear surface. The Golgi 

 apparatus in phytoflagellates is not known to be intimately linked 

 to the rhizoplast, where the latter has been found, but it always 

 occurs in its near vicinity. Since striated kinetosome-linked fibrils 

 are also common in metazoan and metaphytan flagellated cells 

 and, as we shall see, in ciliates, it is safe to say that genesis of 

 fibrils with a periodic structure is a common capacity of the 

 kinetosomal and in some cases centriolar region. Their signifi- 

 cance is in all instances unknown, but certain obvious possibilities 

 come to mind. Considering their positions in various cells and 

 also their suggestive resemblance to the periodic structure of 

 collagen fibrils, one might suppose that they are elastic, sup- 

 porting, or anchoring structures. Their frequent association with 

 the nucleus suggests in addition a role in the establishment or 

 maintenance of essential spatial and temporal relationships 

 preceding mitosis. 



The second common type of kinetosome-linked fibril is a 

 cylindrical structure with a low-density core and dense periphery 

 — described for the sake of convenience as tubular. Its diameter 

 varies from 18 to 25 m/x; it is similar in size and appearance to 

 the individual subfibrils of the flagellum but apparently is never 

 a direct continuation of these. Lateral linkage to kinetosomes 

 has been demonstrated clearly in Euglena and in Bodo; in several 

 other flagellate species tubular fibrils are conspicuously present 

 under the cell membrane, and we do not know whether they are 

 connected to kinetosomes. Similar fibrils that appear to lack a 

 direct kinetosome linkage compose the contractile axostyle of 

 Vyrsonympha and the rodorgan of Peranema. Fibrils that occur in 

 the axostyles of Tritrichomonas, Joenia, and Foaina seem to be 

 slenderer; most authors have not given measurements, but Grasse 

 states that they are finer, and estimates from published micro- 

 graphs average about 15 m^. All reports that include relevant 

 information indicate that these axostylar filaments do not make 

 contact with the kinetosome/centriole directly, but may be linked 

 to it by striated ribbons. Since tubular fibrils occur widely among 

 the ciliates, it will be more appropriate to reserve speculation on 

 their significance until after examining this group. 



Grimstone's (1961) tantalizing announcement of the discovery 



