KEPTILIAN SPERMATOGENESIS 295 



for the tetrads to separate in the plane in which they will be 

 divided later. One of the macro-chromosomes appears as 

 bivalent. 



Side views of the first maturation division very rarely show 

 the condition reproduced in figure 40. The presence of a bipar- 

 tite chromosome at one pole strongly suggests a condition similar 

 to that found in the other lizards studied^ but I am unable to 

 state definitely whether or not we see the true X-element in 

 figure 40. Late anaphase stages show the conditions reproduced 

 in figures 41 to 43. In figure 41 we see a pair of chromosomes 

 projecting out from the upper pole of the cell. Figures 42 and 

 43 show six large chromosomes at the upper pole and five chro- 

 mosomes at the lower pole, the additional element at the upper 

 pole being marked X. (Fig. 43 is taken from poorly preserved 

 material.) This condition would indicate that an X-chromosome 

 is present in Holbrookia and that it goes undivided to one pole 

 in the first maturation division just as was found in the other 

 lizards described. 



The evidence from the second spermatocyte division bears 

 out the conclusions drawn from the first division. Figure 44 

 shows a side view of a spindle, in which one sees the precocious 

 splitting of the chromosomes. Figure 45 is an equatorial plate 

 view showing five maero-chromosomes, and figure 47 is a late 

 anaphase showing five macro-chromosomes going to each sper- 

 matid. (In figs. 47 and 48 the cells were viewed from -one end, 

 so in order to show both poles the cells were shifted with the 

 mechanical stage after one pole was drawn.) Figure 46 shows a 

 cell with six macro-chromosomes, and in figure 48 we have a 

 late anaphase in which six macro-chromosomes are seen distinctly 

 going into each spermatid. 



From this study it is clear that the spermatogenesis of Hol- 

 brookia texana differs in no essential respect from what was 

 found for Anolis and Sceloporus. 



