DAVIS: SPERMATOGENESIS. 131 
somes, but to which McClung makes no reference. However, in 
the forms upon which this author worked, it is difficult to demonstrate 
satisfactorily the sequence of the divisions, and I was myself for some 
time uncertain on this point. But in Stenobothrus I believe there 
can be little doubt that the arms of the large loops are separated during 
the first mitosis. McClung himself has later (:05) described a pre- 
reduction in certain chromosomes of various Orthoptera. In several 
of the Acrididae and one Locustid the monosome becomes attached 
to the end of a bivalent autosome during the prophase of the first 
division, and in such cases the autosome divides reductionally during 
the following division, although McClung still maintains that the 
remaining autosomes divide equationally. It is significant that in 
the autosome in which he finds a prereduction the free ends of the 
univalent components are so clearly marked that there can be no 
room for doubt on this point. In Mermiria this author finds that the 
element formed by the fusion of the monosome and a bivalent auto- 
some end to end later unites with another bivalent autosome and 
that, “Upon the separation of the chromosomes in the metaphase the 
multiple chromosome is divided so that to one pole there goes a triva- 
lent element and to the other a bivalent one, the difference in valence 
being due to the presence of the accessory chromosome in one daughter 
cell. There occurs here an entirely unique separation of chromosomes, 
for by means of it entire tetrads pass into the second spermatocytes.” 
Such a division seems very improbable and requires much more con- 
clusive proof than this author has been able to bring forward. A 
comparison of his Figure 12 with Figure 91 (Plate 6) of the present 
paper suggests that the “multiple chromosomes” of Mermiria may 
be capable of a different interpretation. ‘This seems more probable 
when we remember that Mermiria and Stenobothrus are members 
of the same sub-family, the Tryxalinae. At another place in the 
same paper McClung refers to the unsymmetrical character of the 
daughter elements derived from the division of the multiple chromo- 
some as follows: ‘Among the uncertainties in my mind concerning 
the behavior of the chromosomes in Mermiria, is one relating to the 
nature of the association of the chromosome into the multiple element 
of the first spermatocyte. The tetrads seem of the usual type, 1. e. 
have simple chromosomes of equal size, but when the dyad divides 
it would appear as though there were some heterogeneity present. 
for in the anaphase one limb of the loop is longer than the other. 
‘This may be due to the formation of a multiple chromosome partly 
from the accessory chromosome; otherwise it means that the tetrad 
