ORTHOPTERAN SPERMATOGENESIS 671 



tion of the chromatids to follow from these changed circumstances. 

 While there may be a period of equilibrium established at the 

 metaphase the character of the chromosomal movements does 

 not, materially alter. 



b. Movements of chromatids in metaphase 



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The metaphase movements of the chromosomes have given 

 rise to the most contradictory accounts, due often to the lack of an 

 exact acquaintance with the real structure of the tetrads, but 

 more frequently to erroneous interpretation of the optical images 

 produced by the homogeneous and more or less translucent 

 chromosomes. I shall therefore first consider the various forms 

 of chromosome's, the movements of their chromatids, their rela- 

 tion to the spindle fibers, and will then attempt an interpretation 

 of the accounts given by other investigators. 



The simple, unaltered, rod-shaped form is rarely seen in the 

 metaphase for the reason that, as the chromosomes take their 

 position in the equatorial plate, the points to which the fibers 

 attach approach nearer the center, leaving the free ends to be 

 drawn closer together at the periphery of the cell, as is shown typi- 

 cally in figures 2, 33, 46 and 92. While the statement is true 

 regarding the infrequency of this form of chromosome viewed 

 from the pole of the spindle in early metaphase, the opposite is 

 the fact when chromosomes are regarded laterally in late meta- 

 phase or early anaphase. Under these conditions practically all 

 the elements of the equatorial plate are long, rod-shaped chromo- 

 somes extended in the axis of the spindle. No matter, what may 

 have been the shapes of the chromosomes at the beginning of 

 the metaphase they all are drawn out into rods just before they 

 separate on their way to the opposite poles of the spindle. Lateral 

 views of these conditions are represented in figures 8, 9, 10, 78, 

 96 and 97 where the complexes are extended in a line. That the 

 same chromosome of two complexes may show itself lying in the 

 equatorial plate in one and elongated at right angles to this posi- 

 tion in the other may be seen by comparison of these groups. 



