CHROMOSOME STUDIES IN TETTIGID/E. 



to end union. Figures 23 and 24 show successive stages in the 

 formation of the primary spermatocyte chromosomes. As the 

 chromosomes become more compact in appearance the nuclear 

 membrane disappears and there is no definite boundary again 

 between the nucleus and cytoplasm (Fig. 24). 



During all these changes there has not been the least appear- 

 ance of a side by side pairing of the chromosomes, neither has 

 there been any indication of a longitudinal splitting of the chro- 

 matin material either as chromosomes or as a chromatin thread. 

 With the breaking up of the chromatin thread always more 

 than the haploid number of chromatin elements may be seen, 

 and in many instances there is evidently the cliploid number. 

 This surely justifies the conclusion that at the end of the growth 

 period previous to the formation of the primary spermatocyte 

 chromosomes there appears the diploid number of chromosomes 

 and that the real pairing of the chromosomes does not take place 

 in the spireme stage. It seems, also, very evident that the union 

 of the chromosomes is by telosynapsis. As was previously stated 

 (Harman '15), the dumb-bell shape of the chromosomes is not 

 due to the manner of the division of the chromosomes, but is a 

 result of the way they are formed. This shape is noticed in 

 some of the chromosomes even before the entire chromatin 

 thread is broken up (Fig. 21), and certainly before the first 

 spermatocyte spindle is formed (Fig. 24). 



3. Spermatocyte Divisions. 



There are six dumb-bell shaped bivalent chromosomes and 

 an ovoid univalent chromosome in the primary spermatocyte. 

 These arrange themselves longitudinally on a large spindle (Figs. 

 25 and 26). The univalent, or X-chromosome, lies near the 

 periphery of the spindle. The other chromosomes are crowded 

 toward the center. Most often they are so closely crowded 

 together that it is difficult to see them all at once in a lateral 

 view of the spindle. Always one of the medium-sized chromo- 

 somes lies very near the second-largest chromosome (Figs. 26 

 and 30). 



In the first division all the bivalent chromosomes divide at 

 the constricted part of the dumb-bell (Fig. 27). In other words, 



