DAVIS: SPERMATOGENESIS. 143 
that two homologous chromosomes shall not enter the same spermatid 
or mature ege¢. 
Finally I may point out that the behavior of the chromosomes in 
the Orthoptera during spermatogenesis is fully in accord with the 
Mendelian law of alternative inheritance, as has been pointed out by 
Sutton (:03). 
7. Tue METAMORPHOSIS OF THE SPERMATID. 
One of the most surprising results has been to find such a great 
difference between the Acrididae and the Locustidae in the meta- 
morphosis of the spermatids. ‘The fact that the spermatids of two 
such closely related families differ so markedly during metamorphosis 
would seem to indicate that the details of the process can have no 
fundamental significance. It does not seem best therefore to attempt 
any wide comparisons, since they would appear to be of doubtful 
value. One of the most common and characteristic structures of the 
spermatids is the so called Nebenkern, yet in the Acrididae its history 
is very different from that of a similar element in Steiroxys. But it 
may be argued that the Nebenkerne in the two cases are not homolo- 
gous structures. Possibly — very probably — they are not, but the 
point which I wish to emphasize.is that in the early spermatids we have 
in both cases structures which appear the same, and no one examining 
the spermatids at this time would hesitate, I think, to conclude that 
they are similar structures. Yet it is very certain that later the 
Nebenkern in the Acrididae becomes converted into a sheath sur- 
rounding the axial filament, while in Steiroxys after a complicated 
metamorphosis, it forms the acrosome. Unfortunately I have not 
been able to determine the origin of the Nebenkern in Steiroxys and 
it may be that Steiroxys differs in this respect from the Acrididae. 
However, I hope later by comparison with other forms to clear up this 
point. Meanwhile, the metamorphosis of the spermatids in Locusta 
as described by Otte (:06*) leads to some interesting suggestions. 
This author found that in Locusta the mitochondrion forms in the 
spermatocytes a distinct body, which usually shows an annular differ- 
entiation. During the prophase of the first division it divides into a 
number of small bodies, which are irregularly distributed to the daugh- 
ter cells. In the spermatids most of the mitochondrion collects into 
a compact “‘Mitochondrienkérper”’ (Nebenkern). Meanwhile the in- 
terzonal filaments, witb possibly part of the mitochondrion, become 
