298 THOS. H. MONTGOMERY, 



During the spermatogonic metakinesis and later stages the yolk 

 globules gradually change their position to the equator of the cell 

 (Fig, 56); or probably more correctly speaking, they are propelled, 

 either by a cytoplasmic flowing, or if such exist (though they cannot 

 be seen) by a pushing on the part of pole fibres. 



The connective fibres, those threads which in the metakinesis 

 become stretched out between corresponding daughter chromosomes 

 (Figs. 44—48), are, as we have seen, derivatives of the linin spirem, 

 and are evidently derived from that portion of the linin spirem con- 

 tained in the chromosomes themselves. These fibres begin to dis- 

 appear (Figs. 56 — 58, 60—63) about the time of the formation of the 

 nuclear membranes in the daughter cells, disappearing first in the 

 nuclear region and last at the equator (distal pole) of the cell (Fig. 65, 

 Plate 20). During metakinesis these fibres are approximately all 

 parallel to the axis of the spindle (Figs. 47, 48). Later there appears 

 at the equator of each (?) fibre a thickening, a minute "Zwischen- 

 körperchen" (Figs. 56-58, 60, 61, 63, Plate 19; Figs. 65, 70—72, 

 74, 75, 77, Plate 20); a section through the equatorial plane in this 

 stage shows that these thickenings compose a plate and not a ring. 



The division of the cell body commences in the early anaphase 

 by an annular constriction in the plane of the equator (Fig. 57, 

 Plate 19); during this process there is no cell plate formed. The 

 constriction pushes in as far as the spindle plate (composed of the 

 equatorial thickening of the connective fibres), and then gradually 

 pushes inward the spindle plate, and as a result of this pushing the 

 equatorial portions of the connective fibres are forced inwards (Figs. 56 

 — 58, 60, 61, 63). Concomitantly the more peripheral of the Zwischen- 

 körperchen become pushed against the more central ones ; and the 

 apparent greater size of the more peripheral Zwischenkörperchen is 

 seemingly due to a number being forced into close contact together; 

 no case was noticed, how^ever, where these separate corpuscles had 

 become so closely approximated as to give the appearance of a single 

 large corpuscle. The daughter cells (1st spermatocytes) do not im- 

 mediately constrict off completely from one another, but remain con- 

 nected by the spindle plate through the anaphase to the commencement 

 of the telophase (Plate 20, Figs. 65, 70—72, 74, 75, 77, 80, 97); in 

 one case the connecting plate was apparent in a resting spermatocyte. 

 This long persistence of the Zwischenkörper plate aids in determining 

 the axes of the cell body : it, together with the mass of 3'^olk globules, 

 marks the distal pole of the cell. 



