ORTHOPTERAN SPERMATOGENESIS 675 



in the equatorial plate and guides the passage of the chromatids 

 in their divergence. The result is that all of the chromosomes 

 take up such a position that the synaptic points lie toward, or 

 near, the spindle axis, and all of the chromatids execute like con- 

 vergent movements toward their respective spindle poles. The 

 position that the chromosomes take ipi the first spermatocyte 

 metaphase and the position of their fiber attachment are seen, 

 by a comparison with an equatorial plate of the spermatogonium, 

 to be the same in both generations, the sole difference being that 

 in the earher generation each chromosome is free and independent 

 while in the later they are joined by their corresponding inner 

 ends into pairs. These conditions are clearly evident from a 

 consideration of the two stages in a form like Mecostethus, as 

 may be seen by comparing figure 44, representing a polar view of 

 a spermatogonia! complex, and figure 43 showing a like aspect of 

 a first spermatocyte group. There are the same twenty-three 

 elements in the same relative positions to the spindle and fibers, 

 the one difference being the pairwise union. 



From all these facts it is reasonable and fair to conclude that 

 there is a typical organization of the tetrad which extends even 

 to the relation which it bears to the archoplasm. In Hippiscus 

 and most other Acridians this is of the character just described, 

 but there are a few exceptions and these are of particular interest 

 because of the strong evidence they give regarding precision of 

 chromosome organization. 



(2) In Stenobothrus, Chorthippus, Chloealtis and Trimero- 

 tropis are found conditions that differ somewhat from the account 

 which I have just given as characteristic of the Acrididae. These 

 differences, at first suggestive of underlying, essential changes in 

 type, are found on careful study not to be such, but only individual 

 modifications of certain features by a few chromosomes. The 

 same precision of organization obtains, but details are modified. 

 Apparently the differences are due to changes in the position of 

 the fiber attachments, but whether this is the result of inner struc- 

 tural modification of the chromosomes themselves or whether it 

 is an archoplasmic change does not appear with certainty. Con- 

 sidering all the intrinsic permutations of the chromosomes, it 



