PSEUDOSPORA VOLVOCIS, CIENKOWSKI. 221 
faintly staining granules towards the periphery; these are 
possibly derived from the rays. Towards the equator of the 
oval lies the chromatin separated out from the karyosome. 
In the next stage (fig. 8) the nucleus shows the completely 
developed spindle. There is now no sign of the faintly stain- 
ing granules described in the prophase. ‘The spindle seems 
to be formed entirely from the achromatic intra-nuclear 
elements. ‘I'he chromatin has now formed separate chromo- 
somes, which appear to be rod-shaped, though from their 
small size and highly refringent character it is difficult to 
make certain of this; they are arranged round the equator 
of the spindle. The chromosomes now move apart (fig. 9 a), 
leaving the central fibres exposed. Finally the space occupied 
by these fibres is nipped across (fig. 9b), and the two nuclei 
are completely separated. Each nucleus soon shows the 
karyosome (fig. 10), somewhat irregular in shape, mainly 
composed of deeply staining masses of chromatin, which ap- 
pear to surround the remains of the achromatic spindle. ‘lhe 
rays are not, as a rule, visible at this stage. Shortly after- 
wards the whole animal divides (fig. 11). This frequently 
occurs before the nuclei have quite reached the resting state. 
After a time the Pseudospora leaves the colony (fig. 12) and 
swims away in the flagellate condition. If, as is often the 
case, the ameeboid form has retained its flagella, it now with- 
draws its pseudopodia and becomes oval or oblong. In the 
case of the non-flagellate individuals, the flagella can some- 
times be seen to develop gradually from fine elongated 
pseudopodia ; more often they seem to arise directly without 
any obvious pseudopodial stage. ‘The shape of the animal is 
often very irregular for some time after the flagella are formed ; 
finally, however, the creature completely withdraws its pseudo- 
podia. The nucleus always comes to lie directly behind the 
insertion of the flagella. 
The method of leaving the Volvox is very constant; the 
creature approaches the periphery of the colony and pierces 
through the jelly by means of pseudopodia. The protoplasm 
then flows into the pseudopodia until the creature is hour- 
