HEREDITY IN THE PROTOZOA 303 
favorable to the view that the differences observed 
are in reality failures or imperfections in the 
processes taking place at this critical period. 
This discussion is based on the assumption that 
reduction occurs after separation. If on the other 
hand, reduction of the chromosome number has 
taken place in the two parental individuals in the 
division immediately prior to interchange of micro- 
nuclei, then the two daughter individuals after 
interchange might be supposed to contain different 
hereditary complexes, but unless some further re- 
duction takes place the four granddaughters from 
each ex-conjugant would be expected to give identi- 
cal lines. In that case the evidence mentioned 
above would appear to prove too much, for only two 
different combinations are expected, not four or 
eight. 
Something like reduction must occur somewhere 
if the chromosomes have the same values as in 
higher forms, for, if not, their number would steadily 
increase. An obvious objection to the hypothesis 
that the reduction occurs immediately after conju- 
gation, is that it is purely speculative, for nothing 
peculiar in the division of the two micronuclei after 
conjugation has been observed. The divisions 
appear like ordinary divisions. Evidence as to 
whether the last nuclear division just before conju- 
gation is reductional, or not, ought to be obtained 
from the history of so-called split-pairs. Jennings 
separated in many cases two individuals of the same 
line that were about to conjugate and recorded 
