THE SPERMATOGEM SIS <r I M I ; k \ I.IMI. 



so closely that they cannot be counted. The late mel.ipli.ise or 

 early anaphase spindles (Fig. 43) viewed from the side exhibit 

 no unusual behavior of the chromosomes. No odd or lagging 

 chromosomes are to be seen. The dyads are halved or pulled 

 apart apparently along the longitudinal split indicated in the 

 tetrads of the previous primary spermatocyte, and eleven small 

 univalent chromosomes go to each daughter cell or spermatid. 

 Pig. 44 shows a late anaphase in which chromosomes may be 

 seen in a univalent condition. 



NUCLEAR CHANGES OCCURRING DURING TRANSFORMATION 



OF THE SPERMATIC. 



The resting spermatids are approximately one half the size of 

 the secondary spermatocytes. Only the nuclear behavior of the 

 transforming spermatid will be considered. No attempt has been 

 made to work out in detail the part taken by the cytoplasm 

 or centrosomes in the process. A prolonged period ensues be- 

 tween the resting phase of the spermatid (Fig. 45) and the 

 mature spermatozoan. At the beginning of spermiogenesis the 

 chromatin collects along the linin of the nucleus in a rather 

 scattered condition in which roughly seven to eleven chromatin 

 masses (Fig. 46) may be distinguished. At the same time this 

 initial condensation of the chromatin masses on the linin net- 

 work of the cell is occurring, the axial filament begins to form. 

 The tail, developed to about its full length, is present shortly 

 thereafter. As the chromatin masses appear on the linin of 

 the nucleus, their behavior is indicative of the formation of 

 chromosomes for the metaphase of another division but before 

 this process goes far the chromatin begins to migrate toward the 

 periphery of the nucleus (Figs. 46 and 47). At this stage, 

 scattered around the nuclear membrane, may be seen roughly 

 five dense chromatin masses (Figs. 47 and 48), about twice as 

 large as those which were visible in the more diffuse condition. 

 These chromatin masses, up to and throughout this phase, 

 remain connected by lighter staining strands with the linin of the 

 nucleus. The appearance is that of a fusion of the smaller 

 chromatin bodies of the previous stage in pairs. Following this 

 condition there is a dense massing of the chromatin material 



