326 Wager . — On the Presence of 
apex of the nucleus, as a light blue homogeneous mass more 
or less spherical in outline. This gradually becomes more and 
more irregular until it can only with difficulty be distinguished 
from the surrounding protoplasm, and finally it also disappears 
(Figs. 13 and 14). 
Shortly after this the spindle-figure appears with the two 
centrosomes, one at each end. It is difficult to understand 
exactly how this takes place. Hermann’s description of the 
process as it occurs in the Salamander and Proteus is very 
suggestive 1 . He points out that in the archoplasmic mass at 
first no centrosome could be seen, but when the nucleus gets 
to the stage when the threads begin to split longitudinally, the 
structure of the archoplasm becomes clearer, and one can then 
distinctly make out two centrosomes which repel one another, 
and between them is the young spindle. As the spindle 
increases in size, threads radiate out to the chromatic elements 
and come into contact with them. The spindle and radiating 
threads are thus gradually formed out of the archoplasmic 
body. 
Lauterborn 2 has described a very interesting case of spindle- 
formation in a Diatom, The structure which corresponds to 
the nuclear spindle proceeds from a body which exists beside 
the centrosome. This body however, according to the author, 
might arise from the centrosome, and he proposes to compare 
it with the £ Nebenkern ’ of animals. 
Something of the kind described by Hermann may take 
place in A. galericulatus. The spindle is probably formed out 
of the substance of the archoplasmic body as this becomes 
invisible. The centrosomes appear first, and from these start 
the radiating threads, some of which form a spindle, and some 
come into contact with the chromatic elements (Figs. 15 and 16). 
The chromatic elements then take up their position at the 
equator of the spindle to form the equatorial plate. The 
centrosomes at this stage are very clearly defined as small 
spherical bodies, stained blue. The spindle-threads are also 
stained blue. The centrosomes remain visible during the 
1 Loc. cit. 
2 Loc. cit. 
