Opalina. 241 
a 
\ 
WA / 
x 
Text Fig. III. Outline drawings of O. obtrigona showing the irregular divisions 
in the spring, previous to the formation of the infection cysts. In each figure the 
anterior end is uppermost. Transverse division A—H and M—P. Oblique 
division Y. Longitudinal division beginning as a perforation of the central part 
of the body Y. Longitudinal division beginning at the posterior end of the 
body X. Three divisions occurring at the same time O, Q. 
