SYNAPSIS AND CHROMOSOME ORGANIZATION 481 



spend in all essentials to the series of changes found to occur for 

 chromosome A in Phrynotettix (see '16, fig. 62, plate 6), and 

 would indicate an equational division. Other interpretations, 

 indicating a reductional di\dsion are, of course, possible, and 

 cannot be excluded. 



In chromosome 6 a similar series of stages may be traced. 

 In cell B the split running through most of the length of the 

 element from the right is probably the primary split, while that 

 just beginning at the left and extending to point a would be the 

 secondary split. A continuation of the secondary split and a 

 separation along its plane would give rise to such a stage as 

 that seen in cell C, or, if the separation were delayed, to that in 

 cell D. A rotation of the arms of the tetrad in cell C would 

 give rise to a stage such as is shown in cells E and G, while a 

 similar rotation of the arms of the example in cell D would give 

 rise to the condition seen in F. 



It is regrettable that the polar granules, which do occur to 

 some extent, are not sufficiently differentiated by the staining 

 method used to make the orientation of the tetrads certain. 

 In sectioned material stained with iron-haematoxylin polar 

 gi-anules are, in fact, better differentiated than in the safranin 

 stained smear, but in this instance little study has been made 

 of sections, where identification of all the chromosomes is not 

 so certain. 



In the case of the pairs of atelomitic chromosomes (nos. 7, 

 8, and 9) variations in rate and extent of chromatid movement 

 are not so apparent in the examples drawn on plate 1. Such 

 variations do exist, however, as will be seen by comparing num- 

 ber 8 mth three 'rings' in cell C, and two 'rings' in cells D, E, 

 and F, and figures 9 to 14, plate 3. 



/. The apical constrictions and the chromomere-vesicles. In 

 these atelomitic chromosomes the synaptic point is in many 

 cases very clearly marked by a constriction, as Robertson ('16), 

 has emphasized. This constriction (point h in the figures, plate 

 1) is not visible in all cases, as is indicated in the figures. Chro- 

 mosome 9 in cell E for example, shows scarcely any evidence of 

 a constriction, although it is plain enough in chromosomes 7 



