The Spermatogenesis in Pentatoma up to the Formation of the Spermatid. 59 



necessarily be produced at one end of each chromosome (Fig. A b, in 

 which, as in Fig, Bb, the dotied lines represent the new set of mantle 

 fibres). By the third thinkable mode, when the centrosome divides 

 one daughter centrosome would retain all the mantle fibres, while a 

 secondary set of mantle fibres must become developed and attached 

 to the other daughter centrosome (Figs. B a, Bb). But I think it 

 most probable that the mode of transposition of the mantle fibres 

 in raetakinesis which occur in Pentatoma (Figs. 192—195, 197 — 204) 

 will also be found to occur in other spermatocytic divisions, at least 

 for those cases, where in the monaster of the 1st spermatocyte there 

 are 2 mantle fibres attached to each end of each chromosome. 



To return to the chromosomes, the early metakinesis of which 

 has been described. By the tension of the mantle fibres the daughter 

 chromosomes are pulled to opposite poles of the spindle, which latter 

 elongates markedly during metakinesis. Before the chromosomes have 

 reached the poles of the spindle, they gradually elongate, not simul- 

 taneously however, with their long axes parallel to the axis of the 

 spindle (Figs. 193—199). And now a fact may be determined, which 

 is of the greatest importance in estimating the morphological value 

 of the second division of the chromosomes. While the latter are still 

 parallel to the axis of the spindle, there may be clearly seen in some 

 cases a transverse constriction on some of the chromosomes, so that 

 they already acquire a dumbbell shape (Figs. 194, 196 — 198). These 

 constrictions do not appear on all simultaneously, nor yet are they 

 always to be seen at this early stage; but the fact that these con- 

 strictions frequently appear as early as this stage, shows that these 

 must be undoubtedly the same transverse constrictions as those which 

 are found on all the chromosomes of the 2nd spermatocytic dyaster. 

 When the daughter chromosomes have reached the poles of the spindle, 

 i. e. in the dyaster stage, each of them is of a shortened dumbbell 

 shape (Figs. 200, 201, 206—212). Since they do not all lie in the 

 same plane, some of them become cross sectioned in the preparations, 

 and then appear spherical ; but from a careful examination ot numerous 

 cells, it appears without doubt that all the chromosomes are trans- 

 versely constricted in the dyaster stage. In the completed dyaster 

 stage, when the centrosomes of each 2nd spermatocyte are at opposite 

 poles of the cell, all the chromosomes are pulled, by the tension of 

 the mantle fibres, into a plane perpendicular to the axis of the former 

 spindle (Figs. 201, 203 — 206); and then it is necessary, in order to 



