ABNORMAL MITOSES IN SPERM ATOGENESIS. 191 







ily distinguished ; and as examination of Fig. 7 will show, there 

 are two 1" chromosomes (the very small ones) instead of the 

 usual one (compare Montgomery, '11, Fig. 2). It is, I think, 

 fair to assume that the other chromosomes arc similarly repre- 

 sented in a duplex manner, an assumption which accords with 

 the view now generally accepted of the nature of tetraploid 

 chromosome groups. 



Synapsis is apparently accomplished in a normal manner, and 

 after the " diplotene " threads have become spread throughout 1 

 the nucleus it is possible, in favorable places, to see that the threads 

 are arranged in pairs and not in quartets as one might conceivably 

 expect. In other words the homologous chromosomes are paired 

 off just as they would have been in the presence of the diploid 

 chromosome number, except that in each tetraploid nucleus there 

 are two similar pairs instead of one. During the so-called con- 

 fused period, when the chromatin threads become indistinct, the 

 sex chromosome nucleoli stand out with great clearness. \\ e 

 should expect in a tetraploid nucleus four such nucleoli (barring 

 possible fusions such as sometimes normally occur), representing 

 two X (larger) and two Y (smaller) chromosomes. This ex- 

 pectation is exactly realized (Fig. 8), another bit of evidence 

 which tends to prove that we are dealing here with a case of true 

 tetraploidy. 



When the chromosome tetrads condense in the prophases of 

 the first maturation division, they resemble in every way the 

 tetrads of the normal spermatocytes. (Compare Fig. 9 with 

 Montgomery Cii), Figs. 86, 88 and 93.) It is clear beyond 

 question that homologous chromosomes have paired off in a per- 

 fectly normal manner. These tetrads become condensed in the 

 usual way to form the definitive chromosomes of the first matura- 

 tion division, and the spindle of this division, when seen in side 

 view (Fig. 10), presents no unusual features (except of course 

 for the chromosome number). There happened to be one cyst 

 of cells in various phases of the first spermatocyte division and 

 these dividing cells have been carefully studied. I have been able 

 to find nothing in the manner of spindle formation or chromosome 

 division in any way abnormal, except that the plates have the 

 diploid rather than the haploid number of chromosomes. This 



