The Spermatogenesis in Pentatoma up to the Formation of the Spermatid. 53 



Drüner ('94) also found that the number of these fibres is most 

 abundant at the time of their first appearance. They now seem 

 homogeneous. 



In the early prophases the chromatin nucleolus becomes rounded, 

 but at first retains its central clearer globule. At the loose spirem 

 stage it commences to grow smaller, at the same time losing the 

 central globule (n. 2, Figs. 104, 105). This decrease in dimension 

 continues until it has become smaller than any of the chromosomes 

 (from Fig. 123 on); and is probably due mainly to dissolution of its 

 substance in the nuclear sap , and not to segmentation , for though 

 fragmentation of it occurs, as is proved by the number of small portions 

 scattered occasionally through the nucleus (cf. the Figs. 124 — 149), 

 still the volume of these taken altogether does not equal the volume 

 of the original one. The decrease in size continues until the end of 

 the loose spirem, when a dimension is attained which is approximately 

 uniform for the chromatin nucleoli of all cells; one or more of the 

 smaller bodies, which arose as fragments of the original chromatin 

 nucleolus, may still be seen in the nucleus, and often up to the 

 monaster stage. At the time when the chromosome have attained 

 their definitive form, it usually becomes likewise elongated and dumb- 

 bell-shaped (n.2, Figs. 131, 143, 144, 152, 157); in the majority of 

 cases it appears to assume this form before the nuclear membrane 

 disappears. Thus it looks like a diminutive chromosome among larger 

 ones. As the true chromosomes now stain with safifranine it likewise 

 resembles them in coloration. This peculiar structure acted like a 

 nucleolus in the rest stage, but in the monaster is destined to lie in 

 the equator among the chromosomes, where it also becomes divided 

 in metakinesis, and so terminates in acting like a chromosome, as at 

 the commencement it had been formed from one. 



b) The 1st spermatocytic monaster. 

 The stage of the monaster is now soon reached, there being but 

 a short period between it and the time of disappearance of the nuclear 

 membrane. Before the chromosomes have been pulled into the equator, 

 and while they are still loosely scattered (Figs. 160—167), one can 

 easily determine the presence of continuous fibres joining the opposite 

 pairs of centrosomes (Figs. 160, 162, 164, 165). There are but a 

 small number of such fibres, at least I have been unable to find 

 more than 5 or 6 to a cell; at first they are irregularly bent, but 

 later probably become straightened out. When the monaster stage 



