CYTOLOGY OF ANISOLABIS MARITIMA BON. 243 



to the other. Figures 40 and 41 represent two anaphase plates 

 of a single cell, similar to that shown in figure 39, but cut through 

 the equatorial zone so that one section contains one plate and the 

 next section its sister. In both plates eleven of the chromosomes, 

 the autosomes, are similar; and the large xx-element in figure 41 

 and the smaller y-element in figure 40 occupy corresponding 

 positions. 



Following the telophase of the first meiotic division there is 

 a definite interkinetic period with the establishment of a well- 

 defined, nuclear membrane (Plate XXVI, fig. 42). The centro- 

 someof the primary spermatocyte telophase remains visible and 

 establishes the spindle of the secondary spermatocytes. The 

 dyads remain rather distinct, deeply staining, block-like masses 

 in the nucleus of the interkinetic stage. 



With the formation of the secondary spermatocyte spindles 

 we now have two distinct types of metaphase plates: those 

 with twelve chromosomes, and those with thirteen (Plate XXVI, 

 figs. 43-47). The twelve chromosome plates consist of 11 dyads 

 and a y-chromosome. The thirteen chromosome plates consist 

 of 11 dyads and two x-chromosomes, which separated from each 

 other during the interkinetic period and are here represented by 

 two discrete elements. Figures 46 and 47 (Plate XXVI) show 

 two pairs of sister second spermatocytes, one in each pair con- 

 taining twelve, and the other thirteen chromosomes. The 

 former figure is taken from a section, the latter from a smear 

 slide. 



Occasionally giant secondary spermatocytes are formed with 

 all the chromatic elements of the first maturation spindle present, 

 the chromosomes having divided but the cytoplasm having 

 failed to do so. Two such metaphase plates are shown in 

 figures 48 and 49 (Plate XXVI) and each has 25, well-defined 

 chromosomes. 



The second maturation mitosis divides all the chromosomes 

 equationally, and they pass to their respective poles without 

 lagging. Figures 50 and 51 represent sister anaphase plates, 

 drawn from a smear slide, and showing an exact correspondence 

 in their chromatic elements. The spermatids (fig. 52) are formed 



