OXNERKLLA MAR IT LM A. 
525 
united by a centrodesmose. Up to this stage (PL 27, fig. 8) 
the animal remains spherical, with a few pseudopodia still 
visible. These are now completely retracted, and the animal 
becomes drawn out into an elongate form. As it does so, the 
daughter-centroplasts draw further apart, but still remain 
connected by their “ centrodesmose,” which occupies the 
centre of the long axis of the body (PI. 27, fig. 9). The 
dividing centroplast at this stage appears, in consequence, as 
a much attenuated dumb-bell. The centrodesmose is an 
excessively fine but quite distinct line. Throughout the 
division of the centroplast the central ends of the axial fibres 
of the pseudopodia are visible, radiating through the cyto- 
plasm exactly like the astral rRys of a centrosome (PI. 27, 
figs. 8, 9). 
The “ centrodesmose ” now vanishes, and the two daughter- 
centroplasts are seen — each surrounded by a few short 
“ astral rays ” — to occupy symmetrical positions at opposite 
ends of the organism. 
During the early stages of the division of the centroplast 
the nucleus increases in size (PI. 27, fig. 8). As the animal 
elongates, the nucleus gradually travels towards the middle 
of the body, until it finally takes up a position midway 
between the two daughter-centroplasts (PI. 27, figs. 8-11). 
During this translocation the nucleus usually has an irregular, 
misshapen appearance (PL 27, figs. 9, 10). Sometimes, also, 
its karyosome becomes fragmented (PL 27, fig. 10). But as 
soon as it reaches its station between the two centroplasts, it 
recovers its spherical form and lies as a large and con- 
spicuous vesicle at the very centre of the whole animal (Pl. 27, 
fig. 11). The karyosome now begins to diminish in size 
(PL 27, figs. 11, 12), and as it does so, the chromatin granules 
in the rest of the nucleus increase in size and number. These 
granules, therefore, are probably formed in part at the expense 
of the karyosome. 
During these nuclear stages, the centroplasts also undergo 
changes. They become more or less elongated in a direction 
transverse to the long axis of the dividing organism (PL 27, 
