1908] YAMANOUCHI— SPERMATOGENESIS AND OOGENESIS 153 



cytoplasm at the opposite sides of the nucleus. The first differen- 

 tiation of the blepharoplasts by stains is very sudden, and they are 

 unexpectedly large, quite surprising in fact, for one would imagine that 

 they should appear at first as very small granules of hardly distin- 

 guishable size. The blepharoplasts move toward the nucleus, and 

 during mitosis they hold positions near the poles of the spindle, without 

 any noticeable increase in size (figs. 14-19). Sometimes (not often) 

 it is observed that the blepharoplasts lie just at the poles of the spindle, 

 but evidently this does not seem to mean that the blepharoplasts func- 

 tion as centrosomes; instead, the blepharoplasts in this case may 

 have happened to be caught accidentally in the focal centers of the 

 spindle. 



In the anaphase of this mitosis 66 or 64 chromosomes are always 

 counted (fig. 20). After the telophase each daughter cell of the 

 spermatid mother cell, or each spermatid, contains a single blepharo- 

 plast, which now lies very close to the concave side of the nucleus. 



When the cell plate is just being completed, a new body appears 

 near the nucleus of the spermatid far away from the blepharoplast 

 (fig. 21). For the sake of convenience, I called this body a Neben- 

 kern in the preliminary note. It should be understood that this term 

 is used simply as a temporary designation, which must be replaced by 

 a more accurate one. The Nebenkern in Nephrodium always appears 

 in the location previously occupied by the central spindle of the last 

 mitosis. This spindle has almost disappeared when the Nebenkern 

 appears. Accordingly, it is not probable that the Nebenkern origi- 

 nates from the spindle. 



The spermatids grow to a certain stage and become almost free from 

 one another, so that the antheridium now contains eight to thirty-two 

 polyhedral or spherical spermatids, with very delicate membranes. 

 During the growth of the nucleus of the spermatids the nuclear reticu- 

 lum becomes transformed into a ragged network, very rich in irregular 

 chromatin clumps, but with scanty branched strand structures. One 

 or two nucleoli are always present (fig. 22). The blepharoplast, a round 

 granule by this time, becomes applied to the nuclear membrane, and 

 the Nebenkern, also a round body a great deal smaller than the bleph- 

 aroplast, lies in various locations within the cytoplasm. 



Now the modification of the blepharoplast begins. While the 



