The spermatogenesis of Peripatus (Peripatopsis) balfouri. 339 



should follow, the observed stages? Certainly resting cells of this 

 volume could not escape detection, but I have never seen any resting 

 spermatogonium of the volume of one of these dividing cells, with a 

 single exception to be described below. 



Now the testis in which these giant cells were most numerous 

 was also the one in which degenerating spermatogonia were most 

 numerous; while in all other testes there were but few of these cells 

 and but few degenerating cells. This leads to the conclusion, which 

 all the observations seem to substantiate, that these giant cells are 

 hypertrophied spermatogonia whose mitosis proceeds normally as far 

 as the beginning of the anaphase, when katalytic atrophy sets in and 

 ends in complete degeneration. We may take as a starting point a 

 normal spermatogonium, the prophases of mitosis of which have pro- 

 ceeded normally up to that point when the chromosomes have acquired 

 their definitive form and number, and when the nuclear membrane 

 has disappeared. If at this stage the cell volume should greatly in- 

 crease (probably by an intussusception of fluid from without), we 

 would have exactly the appearance of a giant spermatogonium, namely 

 great relative volume of the cell body and clear appearance. This is 

 I think what really takes place, namely an abnormal increase in volume 

 towards the end of the prophase. If this were not the case, we 

 should find resting cells of equal volume in the zone of the spermato- 

 gonia, but these are not found. 



In the earliest stages of mitosis of these giant cells the chromo- 

 somes lie irregularly throughout the cell; they have about the same 

 form and appearance, but appear to be shghtly smaller, than those of 

 the normal spermatogonia (Figs. 214—216, Plate 22). Sometimes 

 before their arrangement in the equator each shows the longitudinal 

 split. Their number appears to be the same as in the normal spermato- 

 gonia, but it is difficult to count them exactly owing to the fact that 

 each one of the large cells niay extend over from 3 to 5 sections, so 

 that two successive sections often contain portions of the same chromo- 

 some : this explains why the numbers obtained were somewhat greater 

 than the normal number, 28. In five cells in which they were care- 

 fully counted by drawing, the following numbers were obtained: 28, 

 30, 30, 34, 34. The cell substance appears to be composed to great 

 extent of a thin structureless fluid, in which are suspended delicate 

 fibres and a usually considerable number of yolk globules. The 

 achromatic spindle is exceedingly delicate (as it is in all later stages), 

 more delicate even than in the normal spermatogonia, so that its in- 



22* 



