DAVIS: SPERMATOGENESIS. 143 



that two homologous chromosomes shall not enter the same spermatid 

 or mature egg. 



Finally I may point out that the beha^'ior 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. The 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 xA.crididae. 

 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 "Mitochondrienkorper" (Nebenkern). Meanwhile the in- 

 terzonal filaments, with possibly part of the mitochondrion, become 



