282 ELIZABETH A. SMITH. 



at the point where the transverse constriction of the cytoplasm 

 takes place and a thickened thread results. This is shown in 

 Fig. 64 which is a telophase. Fig. 65 is a drawing from an 

 aceto-carmine smear in which the sex-chromosome stood out 

 plainly at one pole. The centrosomes when present are much 

 smaller than in the preceding division and in many cells they 

 cannot be seen. 



If the first division was reductional as the evidence seems 

 to show, then theoretically this division must be equational. 

 The sex-chromosome passed over undivided and this represents 

 the reduction stage for it, as it divided equally in the first division. 

 In Libellula basalis the sex-chromosome goes over undivided in 

 the first division. Sutton (1900) found also that in Brachystola 

 the sex-chromosome passed over undivided in the first division, 

 so that as regards this element in different species, it is obvious 

 that the place of reduction is not always the same. 



(e) Transformation of the Spermatid. 



At the end of the second maturation division each of the 

 spermatids resulting from one secondary spermatocyte contains 

 a mass of chromatin which never resolves itself into individual 

 chromosomes. In many cases after the two daughter spermatids 

 from one secondary spermatocyte are completely separated, the 

 sex-chromosome stands out distinctly from the chromatin mass 

 in one of the cells as indicated in Figs. 66 and 67. In most 

 spermatids, the sex-chromosome is incorporated into the chroma- 

 tin mass and there is no noticeable difference in the amount of 

 chromatin in the two classes of spermatids. The chromatin 

 becomes broken up into a number of irregular masses, three or 

 more, connected by a faint network containing chromatin 

 nodules at the intersections of the meshes (Figs. 68, 69, 70, 

 and 71). 



At this stage, the centrosome which lies close to the nuclear 

 wall sends out a fine thread w T hich is the axial filament of the 

 tail. The cytoplasm at the end opposite the centrosomes 

 elongates into a head spine which is free from granules and 

 attains a considerable size (Figs. 72 and 73-). Biitschli as far 

 back as '71 described in the spermatozoa of Agrion ptiellce a 



