Horváth Géza (szerk.): A Magyar Természettudományi Múzeum évkönyve 8. (Budapest 1910)
Soós, L.: A Helix arbustorum hím csirasejtjének fejlődése
SPERMIOGEN'ESIS OF HELIX ARBUSTORUM. 313 spheres, reach the poles of the cell, and become connected by a central spindle. The chromosomes still occupy their former position, or they change it but little (Pl. IX., Fig. 9.), but they soon arrange themselves in the equatorial plate of the spindle. I show the metapliase on three figures (Pl. IX., Figs. 6. to 8.), Fig. G. showing a little earlier, Figs. 7. and 8. a somewhat later stage. The chromosomes hying in the equatorial plate are at first irregular in shape like the former, but they become later more regular, ovoidal, and arrange themselves parallel with their longer axes to the axis of the spindle. The chromosomes divide parallel to their longer axes. The division is scarcely to be seen from the side, but it is very evident in sections which show the spindle from the poles. We find the chromosomes on such sections (Pl. X., Fig. 1.) tied. The incision corresponds to the plane of division. The last mentioned figure shows an abnormal cell with two spindles which are at right angles to each other. Such cells are not rarely to be found, and their origin may be led back to the imperfect division of the spermatogonia. The centrosome is well visible on each figure. We see stained on Pl. IX., Fig. 7., which was drawn from a more strongly washed preparation the centriole alone, surrounded by a clear area. This area is equivalent to the centrosphere (s. Pl. IX., Fig. 9.). The centrosphere is on the two other figures stained by the iron hematoxylin ; they are irregular in shape. We can distinguish in the metapliase three kinds of chromosomes : 1. The ordinary chromosomes ; thei r number is, as seen above, with the greatest probability 24 ; 2. two very small chromosomes (Pl. IX., Figs. ('>., 8.) which pass during division into different daughter cells. They take their origin from an unpaired chromosome which can be seen already at the end of the prophase, and which is characterized by its smaller size (PL VIII., Fig. 9., the smallest, spherical chromosome); 3. an unpaired chromosome, or chromosome-like body which at the end of the metaphase becomes cast out into the cytoplasm (Pl. IX., Figs. ('»., 8.). These two latter kinds of chromosomes will be discussed later. The chromosomes after dividing pass to the poles of the spindle (Pl. IX., Fig. 10.). Several chromosomes are longitudinally incised, thus they appear to be divided. It is most probable that this incision indicates the plane of the second maturation division. A similar appearance is to be observed in Enteroxenos, the chromosomes of which, according
