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structure in T. lewisi is difficult to follow. It certainly often 
enters into close contact with the nucleus before division as in 
figs. 15, 16, but it is frequently discernible after the nuclei have divided, 
as in fig. 20. In some of the resulting forms, moreover, when two, 
three, or four nuclei have been produced, the extra-nuclear-centrosomic 
derivative may sometimes still be observed lying between the nuclei, 
and apparently in close association with them. Whether the 
substance of the extra-nuclear-centrosomic derivative is directly 
absorbed by the nuclei, or merely disappears in the cytoplasm, the 
body in question sooner or later vanishes, and cannot be obsen'ed any 
further. The division of the nuclei of T. lejvisi in the form we have 
just described is accompanied by the fission of the extra-nuclear 
centrosome, the fission of this latter body being generally 
accompanied by a movement towards the nucleus. It sometimes 
happens, however, that not only does the extra-nuclear centrosome 
move towards the nucleus, but the nucleus itself also moves towards 
the extra-nuclear centrosome. The advent of division of the extra- 
nuclear centrosome is marked by the development of the rod-like 
form into a flat disc, which perhaps through its thinness stains less 
darkly than the extra-nuclear centrosome when in a condition of rest 
(figs. 40-43.) The next phase is constituted by the collection of the 
staining material on opposite sides of the disc, and finally by the 
production in this way of two curved rod-like bodies on each side of 
the disc {figs. 41, 42). These new rod-like bodies constitute the new 
extra-nuclear centrosomes. They now rapidly diverge; it may be 
widely, showing at first a faint connection, which appears to be the 
remaining substance of the disc that has been simply drawn out This 
connection rapidly disappears, the resulting extra-nuclear centrosomes 
having then the same appearance as those in the parent form ; but 
they are naturally smaller. During the nuclear division at this period 
which result in the production of the multi-nucleated masses, the 
ivision of the extra-nuclear centroseme does not, so far as we have 
been able to see, result directly in a division of the flagellum or the 
body attached to its proximal end. During such phases in T. lewisi, 
the original flagellum and its bead remain unaffected, and apparently 
o nothing. When the extra-nuclear centrosome has divided, as in 
fig. 44 > It is often seen that a small body is closely attached to it, 
appearing as if it had been separated from the extra-nuclear 
