414 ELMER L. SHAFFER. 



will separate in the anaphase at the point of synaptic union and 

 the division is reductional. The other tetrads have terminal 

 spindle fiber attachments, but I am unable to say whether they 

 divide reductionally or equationally. In the case of the CC 

 tetrad, there is evidence that the narrow portion of the dumb-bell 

 actually marks the point of synaptic union, and since separation 

 of the dyads in the anaphase occur at this point, the division is 

 also reductional. 



The sex-chromosome (Fig. 25, X} usually lies on the outer 

 surface of the spindle. In the anaphase it usually lags behind 

 the other dividing chromosomes, sometimes appearing bipartite, 

 and passes undivided to one of the daughter cells (Figs. 27, 70). 

 As the dyads come into the late anaphase of the division, a 

 secondary (equational) split can often be seen (Fig. 27, A A}. 



Following the first maturation division, there is no inter- 

 kinesis or construction of a telophase nucleus. The dyads again 

 become arranged in the metaphase, each showing the secondary 

 split. Figure 28 (also Fig. 58) is that of second spermatocytes 

 (daughter plates), one having 9 dyads the other having 9 dayds 

 plus the X-chromosome. It will be noted that the grouping of 

 the dyads is exactly similar to the grouping of the tetrads in the 

 first maturation division metaphase, namely 8 dyads arranged 

 in a circle around the macrochromosome dyad. In Notonecta, 

 Browne ('16) found that the chromosomes always assumed a 

 definite grouping in the metaphase, but the grouping was different 

 in the two maturation divisions. In the anaphase of the second 

 maturation division all the dyads divide and there are no lagging 

 chromosomes. 



(d) Giant Spermatocytes. It is quite common to find spermato- 

 cytes with double or more the number of chromosomes. Figure 

 59 is a photograph of such a spermatocyte in the metaphase 

 which has over twice the normal number of tetrads. These 

 giant spermatocytes develop normally and give rise to giant 

 spermatids and spermatozoa (Figs. 31, 33<r). The origin of these 

 giant cells may be traced back to the spermatogonia in which 

 there has been a failure of division of the cell-body resulting in 

 cells with double the diploid number of chromosomes. Such 

 cells are quite common among the spermatogonia of the multi- 



