SYNAPSIS AND CHROMOSOME ORGANIZATION 491 



not through the middle. A spUt is seen in the proximal end 

 (at the left) but it cannot be determined whether this represents 

 primary or secondary split; in cell B, however, both sphts are 

 easily seen and it is further observable that the separation at 

 the proximal end (left) is along the plane of the secondary split. 

 The tendency for the proximal gi-anules to diverge with further 

 separation along the secondary split is seen in cell C. In cell 

 D the relation of the chromatids is much the same as in cell B 

 but they are more condensed. In cells E, F, and H, as I have 

 already noted, smaller knobs or enlargements occur at the 

 proximal ends, while a bulging at the middle of the oriented 

 tetrad indicates the larger distal granules. It seems fairly safe, 

 then, to assume that a tetrad in the condition seen in cell C would 

 become oriented in the metaphase without further change in the 

 relationships of the chromatids, except their further separation 

 along the plane of the secondary split. There seems to be good 

 reason for concluding, therefore, that division is equational for 

 this chromosome. 



There is also some e\idence that chromosome number 4 di- 

 vides equationally in this first division. In the metaphase 

 cell E the horizontal components of the chromatids on the right 

 side of the tetrad have stained differently from those on the 

 left. They failed to retain the stain so well and appeared finely 

 granular, as indicated in the dra\\dng, in contrast to the compact, 

 deeply staining chromatids on the left. It is reasonable to sup- 

 pose that those two chromatids which show this peculiarity 

 belong to the same parent chromosome, and, therefore, that 

 halves of chromosomes are being separated in this division, con- 

 stituting an equational di\dsion. Attention may be directed 

 to the cluster of granules attached to this chromosome. In the 

 examples in cells A, B, and C, plate 2, it cannot be determined 

 just what relation this appendage bears to the chromatids. In 

 figures 22 and 23, plate 3, however, it is plainly indicated that 

 the structure is attached to a chromomere of only one of the 

 conjugated threads. Presumably this condition holds true for 

 all stages. If that be true, then these appendages may be at 

 the distal end, if it be permitted to associate the peculiar stain- 



