310 KANSAS UNIVERSITY SCIENCE BULLETIN. 



ZOOLOGICAL LABORATORY. 



stola magna"* make a detailed account of the manner of 

 these divisions in this species unnecessary, since in my ma- 

 terial the divisions display the typical order of the AcrididsB. 



SPERMATOGONIA. 



A polar view of the spermatogonial chromosomes of Phryno- 

 tettix magnus shows twenty-three chromosomes appearing as 

 longitudinally split rods of varying lengths (fig. 1). The ac- 

 cessory chromosome {x) can be distinguished from the others 

 by its rough contour and the more marked hyaline area sur- 

 rounding it. In the succeeding anaphase, division is accom- 

 plished by a separation of the halves of the chromosomes. 

 Separation proceeds from the proximal to the distal end and 

 results in the proximal ends reaching the poles first. The same 

 peculiarities that distinguished the accessory in the metaphase 

 are also observed in this stage (fig. 2 x) . During the ana- 

 phase the cell elongates in the direction of the spindle axis. 

 The chromosomes are drawn close to the opposite ends of the 

 elongating cell and, on account of their number and relative 

 thickness, lie approximately parallel to each other (fig. 3). 

 The spindle between the two groups of chromosomes which 

 are to form the nuclei of new cells persists between the daugh- 

 ter-cells and fades away near the groups of nuclear elements. 

 The subsequent characteristic changes through which the spin- 

 dle remains pass form an excellent criterion in determining 

 the sequence of the various changes which are observed in the 

 cell. As the division wall is formed the spindle is slowly con- 

 tracted. What Sutton describes as a tendency of the daughter- 

 cells "to roll upon one another" is plainly seen from figure 4 

 to be a rolling of the nucleus, which forces the spindle fibers 

 to one side of the cell. The same figure shows this peculiar 

 movement of the nucleus to be accompanied by a disintegra- 

 tion of the chromosomes, which, together with the persistence 

 of the spindle fibers, may bear a causal relation to the former 

 phenomenon. 



As the separation of chromatin granules begins the chromo- 

 somes move apart, retaining, however, their parallel arrange- 

 ment, and each chromosome becomes surrounded by a delicate 

 membrane forming the chromosomal vesicle. The dissocia- 

 tion of chromomeres in the telophase results in the diffusion 

 of the chromatin within the vesicles, which, so far as I have 



* Kansas University Quarterly, vol. 9, No. 2, 1900. 



