420 Sidney 1. Kornhauser 



the other (Fig. 34 «). If now there shoukl be an exchange of portions 

 of the split chromosome, the two short arms would have to fuse and 

 separate themselves froni the two long arms. Thus would arise a raarked 

 variability in the sizes of the chromosomes from one generation to another, 

 and this we know does not exist. The presence of X-, Y-, and V-forms 

 (Fig. 34), all in the same nucleus, and the single chromosome (s, Fig. 35) 

 without a "Querkerbe" argue against symmixis by permutation, which 

 would be possible only if symmetrical X-forms were produced in the 

 interkinetic period. 



The metaphase plates of the second spermatocyte division (Fig. 35) 

 contain twelve chromosomes. In contrast to the first spermatocyte 

 division, counting is not at all difficult, owing to the fact that the chromo- 

 somes (Fig. 36), longitudinally split, lie with their long-axes in the equator, 

 and in such a flat plate, that all can be seen without changing the focus. 

 Eleven of the chromosomes (Fig. 35) show a "Querkerbe", which in at 

 least two is situated nearer one end. The twelfth chromosome (s) is 

 Single and homologous to that seen in the oöcyte (s., Fig. 49). Figure 37 

 shows two sister metaphase plates in the same cytoplasmic mass — their 

 spindles being parallel. Fach plate contains twelve chromosomes. ^\Tieth- 

 er separated or still united, sister second spermatocytes were always 

 found in the same stage. In the division of the second spermatocyte 

 which separates the halves of the longitudinally divided chromosomes 

 equationally, one chromosome is noticeable, which, although split length- 

 wise, lags behind the others (h, Fig. 39); and there are distinct fibers 

 passing from this chromosome to the two groups of anaphase chromo- 

 somes. In Figure 40 is seen a later condition, which is a stage of long 

 duration, judging from the frequency with which such figures are seen. 

 The fact that such a lagging chromosome is found without exception 

 in the anaphase stage of the second spermatocyte division, and always 

 in the same condition in sister cells, points out that we here have to 

 deal with a definite chromosome different from the autosomes. From 

 its behavior in the second maturation mitosis, it may most probably 

 be identified with the lagging pair of the first spermatocyte (Fig. 31), 

 one of which passed to each of the second spermatocytes (Fig. 32). In 

 Hersilia, we have a case comparable to that of the Diptera and Coleoptera 

 (Stevens' 08, '09), namely, a Separation of the hetero-chromosomes in 

 the first spermatocyte mitosis, and a halving of them equationaUy in 

 the second mitosis. The lagging chromosome of the second spermato- 

 cyte (Figs. 39, 40) is not the small single chromosome of Figure 35, which, 

 being morphologically unlike the others and resem])ling the hetero-chromo- 



