480 JEAN REDMAN OLIVER 



tube is that of a 'Faserkorb,' or basket work, similar in form 

 and origin to that described by Meves ('99) for the guinea-pig. 

 These fibrils are at fii-st very short and thin, but they increase 

 in length and thickness rapidly. By the progressive differen- 

 tiation of the cytoplasm between them they soon fuse into a 

 hyaline tube, surrounding the axial thread and open at its lower 

 extremity. In optical section the sides of this tube appear as 

 two strong curved lines as shown in figures 20 to 28. The line 

 of attachment to the nuclear wall is soon marked by a thickening 

 of the edge of the caudal tube, which appears as a rounded knob 

 when seen in optical section (fig. 27). The cytoplasm included 

 within the caudal tube stains more readily also than that por- 

 tion outside of it. Progressively the amount of cytoplasm sur- 

 rounding the caudal tube becomes reduced more and more as 

 the main mass continues its migration toward the lumen of the 

 tubule, soon leaving but little more than the cell membrane 

 investing the nucleus and the caudal tube. 



The nucleus of the spermatid undergoes great changes in this 

 period, which affect both its form and its staining character. 

 The fine granules, into which the irregular clumps of chromatin 

 of the early stages have resolved themselves become still smaller 

 and more uniformly distributed, and give rise to the homogenous 

 appearance characteristic of the adult sperm. The staining 

 character of the nucleus shows marked changes in respect to 

 iron hematoxylin. It now stains very deeply, and loses scarcely 

 any color on differentiation, so that the head has a deep brown 

 or black appearance. In the later stages much of this staining 

 affinity is again lost, so that it appears a light bluish gray. The 

 shape of the nucleus is also steadily changing during this period, 

 a decided flattening becoming more and more evident as develop- 

 ment proceeds, differentiating a dorsal and a ventral surface from 

 the narrowing sides. 



The head cap has been practically completed in the former 

 period, and its further development consists in a flattening and 

 condensation of its earlier form, thus making a more intimate 

 union with the nucleus, extending down over the whole anterior 

 and middle portion of the latter, and thinning away behind to 



