PSEUDOSPORA VOLVOOIS, CIENKOWSKI. 217 
times the length of the individual. A slight depression is in 
some cases to be seen at the point of insertion of the flagella. 
This is, however, not by any means a constant feature. In 
the pear-shaped individuals there is often a blunt process 
about one third of the way from the flagellate end. The 
ectoplasm, endoplasm, and contractile vacuoles show no 
special features. The nucleus is identical with that described 
in the amceboid form, and is situated immediately behind the 
insertion of the flagella. 
Method of swimming.—These flagellate forms swim 
with one flagellum dragged behind—in the cases where the 
flagella are unequal the longer one—the other is lashed out 
in front. The movement of the front flagellum varies slightly ; 
usually the flagellum starts from a position in a straight line 
with the longitudinal axis of the animal, it is rapidly lashed 
to one side, and then slowly returns to its original position. 
This may be repeated either first on one side and then on the 
other or over and over again in the same direction. When 
the flagellum is used in the latter way the creature tends to 
swim in a circle, the flagellum which is dragged behind 
correcting this to a certain extent. The fiagellum is some- 
times passed round the individual, causing it to revolve round 
its longitudinal axis. Occasionally both flagella are used 
with a very rapid vibratile movement. 
C. Radial form. Size, (012 mm. to ‘02 mm. 
The radial Pseudospora (fig. 4) differs considerably in its 
external features from the two previously described forms. 
It is normally a spherical creature with fine radial pseudo- 
podia; these spring most frequently from all parts of the 
animal, though they are at times confined to certain parts. 
The pseudopodia are sometimes three or four times the 
length of the diameter of the creature, and are not always 
equally fine. 
While moving about either in the Volvox colony, or in the 
free condition, the creature frequently temporarily adopts a 
spindle shape (fig. 5) with a number of long pseudopodia at 
