The Spermatogenesis in Pentatoma up to the Fornaation of the Spermatid. 63 



fibres, and there is here no ground for supposing that they are derived 

 from the cytoplasm. At the last stage here described (Figs. 222—224), 

 the nuclear membrane has not yet appeared ; the chromatin mass lies 

 in a clear cavity, from which even the connective fibres have become 

 separated, and around this space is a zone of idiozome substance. 



Without a doubt there are only two reduction divisions, as is 

 proved by the comparative size of the spermatocytes and their con- 

 tained chromosomes. Between these mitoses there is no trace of a 

 rest stage, the spindle rays still persisting, and the chromosomes 

 retaining their original form. Thus the stages between the 1st and 

 the 2nd spermatocytic monasters represent merely a metakinesis and 

 beginning of a dyaster, and hardly the latter. 



D. Summary of the more important observations. 



1) The resting spermatogonia are grouped in the form of rosettes, 

 their cell bodies connected at the centre of the rosette. In the cyto- 

 plasm, at some distance from the nucleus, lies a spherical idiozome, 

 within which centrosomes could not be found in the resting cell. 



2) In the prophase of spermatogonic mitosis , the continuous 

 chromatin thread segments into 14 chromosomes, which are at first 

 elongate, but later assume a nearly spherical form. In the meantime 

 a pair of centrosomes appears in the idiozome, then leaves the 

 idiozome and wanders towards the nucleus; the centrosomes are 

 connected by a central spindle. The central spindle and pole fibres 

 are of cytoplasmic origin, while the mantle fibres are probably to 

 great extent derived from the nuclear linin. The idiozome substance 

 appears to take no part in the formation of spindle fibres, some of it 

 being still present in mitosis. The chromosomes are grouped in a 

 dense plate in the monaster stage, the mantle fibres being attached 

 to each end of each chromosome. 



3) In the metakinesis the 14 nearly spherical chromosomes are 

 halved, but it could not be determined with certainty whether this is 

 a longitudinal division. 14 daughter chromosomes pass into each 

 daughter cell (1st spermatocyte), and shortly afterwards the complete 

 separation of these cells takes place. In the metaphase the chromo- 

 somes do not fuse together. The connective fibres formed in meta- 

 kinesis represent each a hollow cylinder of linin, derived from the 

 linin contained in the chromosomes. 



4) The anaphase of the 1st spermatocytes may be subdivided 

 into 3 well-marked periods : the early anaphase, the synapsis, and the 



