ORTHOPTERAN SPERMATOGENESIS 707 



may therefore be asserted beyond any reasonable doubt that the 

 annular chromosomes of the first spermatocyte prophase are 

 constituted as the great majority of investigators have described 

 and figured them. 



c. Relation of the chromosomes of the first spermatocyte metaphase 

 to those of the prophase 



There is little or no difference of opinion regarding the passage 

 into the metaphase of the chromosome forms found in the pro- 

 phase. With regard to the rings Montgomery states that 

 although they are conmcion in the prophase of Syrbula they occur 

 but rarely in the metaphase. Robertson, however, showed 

 clearly that this was an error. It may therefore be confidently 

 asserted that the structural conditions shown by the prophase 

 chromosomes are carried over into the metaphase, suffering 

 only such modifications as result from continued condensation 

 and possible chromatid movements. 



d. History of the tetrads in the first spermatocyte mitosis 



1. Rod-shaped tetrads. Reference has already been made to 

 the position of the rod-shaped chromosomes in the first spermato- 

 cyte m.etaphase. That rods elongated in the spindle axis occur 

 is not denied by any one; that they occur extended in the equa- 

 torial plate and divide in its plane is, however, disputed. My 

 description of the actual occurrence of rods extended in the plane 

 of the future cleavage and of their subsequent movements has 

 been criticised by Montgomery, Davis and Gregoire as an assump- 

 tion of complicated changes. The case of IVIecostethus is a suffi- 

 cient answer to any such criticism, for here nearly all the chromo- 

 somes lie in the equatorial plate and, since the fibers attach at 

 the middle synaptic points, all the movements of division have 

 to take place by an extension of the axial arms at the expense of 

 the equatorial. Because of the unusual length of some of these 

 chromosomes, however, instead of the chromatids remaining in 

 contact entirely through this transformation, as usual, they sepa- 



