POLYSTOMELLA. 93 
shell or are liberated by the protoplasm creeping out and 
forming a halo of anastomosing threads round the deserted 
test. The spores secrete 
a shell and grow into the 
typical megalospheric forms. 
When the megalospheric 
form is about to reproduce, 
its nucleus disintegrates and 
is replaced by numerous 
scattered nuclei formed 
around chromidia. 
protoplasm segregates into 
little masses, each centred 
in a nucleus. Each of 
these nuclei divides by 
mitosis into two, then into 
four, and the division of 
the nucleus is followed 
by the division of the 
protoplasmic mass, 
The- 
so that hosts of 
e provided with flagella, swim out 
Fic. 37.—Polystomella, megalo- 
spheric form, with large central 
chamber (JZ) and one nucleus 
(W).—After Lister. 
tiny cells are 
Fic. 38.—Polystomella, 
central chamber (c.c.), 
microspheric form, with small 
umerous nuclei (V7), bridges of 
protoplasm between chambers (B).—After Lister. 
