230 Proceedings of Indiana Academy of Science 



and 31. In the secondary spermatocyte there were 69 polar views of 

 the clear metaphase plates. , Of this number 37 showed 13 and 32 

 showed 12 chromosomes (figs. 32, 34 and 35). This is just what 

 would be expected where there were very few cases of the prophase 

 separation of the small univalent and the large bivalent chromosomes 

 (figs. 11 and 12). The metaphase counts alone show very definitely 

 that the univalent chromosome behaves irregularly prior to the second 

 spermatocyte. No lagging chromosomes were seen in this specimen. 



The above evidence leads to the conclusion that the small individual 

 seen in the resting stage and early prophase of the second spermatocyte 

 becomes attached to one side of the large chromosome pair sometime 

 between the metaphase of the spermatogonia! division and the prophase 

 of the primary spermatocyte. Although this attachment has not been 

 observed it probably takes place very early in the growth period. These 

 attached chromosomes form the larger end of the uner^ual pair. Occa- 

 sionally the chromosomes become detached allowing all pairs to divide 

 normally while the univalent chromosome passes undivided to one pole 

 giving the 13 chromosomes in the first spermatocyte metaphase. Nothing 

 can be said with certainty as to the mode of attachment although the 

 small chromosome seems to be plastered to the side of the larger chromo- 

 some so as to show no break in the general outline of the mass except 

 for a slight enlargement (figs. 19 and 20). It might be expected that 

 the attachment of the univalent chi-omosome to one-half of the autosome 

 pair would make a very noticeable enlargement but such was not the 

 case. Figures 17 and 18 show the univalent chromosome unattached but 

 near one of the large autosome pairs. Assuming that the small chromo- 

 some was plastered to the upper half of the large bivalent chromosome 

 the resulting mass would not be greater than the larger end of the 

 unequal pairs shown in figures 19 and 20. After the condensed con- 

 dition in the anaphase of the first spermatocyte division (fig. 29.) the 

 chromosomes separate as individuals from this chromosomal mass and 

 remain separated to divide normally in the secondary spei-matocyte. 

 This accounts for the unusual number of 12 chromosomes in the first 

 spermatocyte and the normal number of 12 and 13 chromo.somes that 

 appears in the second spermatocyte. 



It is interesting to note that the same numerical condition has been 

 found in the distribution of the chromosomes of Anisohibis iiuDitinut 

 by Kornhauser\ 



■. Kornhauser, S. I. Cytolouy of Anisolabis maiitima. Abstract of Papers, American 

 Society of Zoologists 1920. 



