30 ZOOLOGY 
two (8 and 9, and F), and each half divides again (G), so that 
each individual contains four fragments of paranucleus: two at 
one end of the body and two at the other (9). The two at 
Fic. 22.—Diagram of changes undergone by 
paranuclei of Paramoecium aurelia during WP --- 
conjugation. Maupas. 
A. Increase in size of paranuclei. 
B,. 1st division of paranuclei. Gee. 
C. 2nd division of paranuclei, and disappearance 
of seven-eighths. aoe 
D. Division of remaining portion into male and ‘ 
female pronuclei. | eee 
E. Fusion of male and female pronuclei. 
F. Division of fertilised paranucleus into two D ----- 
halves. 
G. Division of these halves. Cc 
H. Of the four quarters shown inG, one forms B 
the new nucleus of young Paramoecium which is 
formed by fission, the other divides into two and 
forms two paranuclei, one in each of the new indi- 
viduals. 
the posterior end undergo no change, and form the paranuclei 
of the new individuals which result from the subsequent 
fission ; the two at the anterior end increase, and are destined 
to form the nuclei of the new individuals (10). Before this 
is completed, however, the two paranuclei have again divided 
Fic. 23.—Opalina ranarum, Ehrb. From Broun. 
1. Nuclei. 
2. Ectoplasm. 
(H), so that after fission each new individual contains one 
nucleus and two paranuclei. 
Whilst the paranucleus of the original Paramoecium has 
been undergoing these changes, the nucleus has first become 
