AN EXTRA DYAD.AND EXTRA TETRAD IN CAMNULA 405 
D. Equational and reductional non-disjunction of the super- 
numeraries 
Reductional non-disjunction of the members of the extra 
tetrad is illustrated in figure 136. Another cell where the two 
dyads of this tetrad were passing to the same pole was observed, 
but not drawn. The apparent failure of the two dyads of the 
extra tetrad to synapse in the complex shown in figure 85 might 
have resulted, too; in reductional non-disjunction. Since the 
publication of the results of Wenrich’s (’16) valuable work on the 
spermatogenesis of Phrynotettix we cannot assume that the first 
or second maturation mitosis is the reduction division for a par- 
ticular chromosome unless we know the history of the element in 
the early prophases of the first division or unless it happens to be 
a tetrad with unequal homologues. Hence, as each of the dyads 
resulting from the above three abnormal kineses would divide 
in the second spermatocyte mitoses, the final outcome with re- 
spect to any one of the twelve spermatids might be either the 
equational or reductional nondisjunction of the supernumerary 
pair. Hence, also in the cell shown in figure 109, where one 
dyad of the extra tetrad has gone to one pole and the other dyad 
is dividing, we may have an instance of either reductional or 
equational non-disjunction. If, so far as the extra tetrad is con- 
cerned, this is a reducing mitosis, we have an instance of a 
unique kind of reductional non-disjunction. This is probably 
the case, for it is likely that the two members of the tetrad 
failed to synapse in this cell, otherwise one dyad would scarcely 
have lagged behind the other chromosome and divided. The 
results of this type of non-disjunction for the second spermato- 
cyte complex formed at the upper pole are seen in figure 115. 
Here we have a second spermatocyte telophase with fourteen 
monads at one pole and thirteen at the other: The second sper- 
matocyte complex derived from the chromosome group at the 
lower pole would be similar to those seen in figures 114 and 117. 
In figure 108, where the two monads of an extra dyad have 
separated in a first spermatocyte division and gone to the same 
pole, we have the basis for equational non-disjunction in the next 
division. For these two monads would undoubtedly have segre- 
