490 D. H. WENRICH 



longer or the shorter ends may become free in advance of the 

 other end. Just why the chromatids should assume the vary- 

 ing relationships to each other in similar stages of the tetrad 

 transformation period is of course not easily determinable, but 

 the metaphase figures seem to be derived from similar ones in 

 the earlier stages wdthout much movement of the chromatids 

 during the later condensed prophases, nor until the forces in 

 metaphase and anaphase are at work. One may suppose that the 

 movement of the chromatids takes place at different rates in 

 different cells and that, as condensation in the later prophases 

 progresses, such movements are retarded; the result being that 

 whatever stage in transformation has been reached in a late 

 prophase is the one in which the element enters the spindle. 

 The further movements then must be the result of the forces in 

 operation during metaphase and anaphase. 



e. The planes of the first division. In Chorthippus, as de- 

 scribed on pages 480 and 481 the evidence seemed to favor an 

 equational division for chromosomes 2, 4, and 6 (plate 1) which 

 are telomitic. E\ddence of equational division among the telo- 

 mitic chromosomes of Trimerotropis can be found on plate 2. 

 Chromosome 2, for example, as it appears in cell A, has a very 

 characteristic arrangement for the parts of this element. It has 

 very pronounced polar granules at both ends, those at the 

 distal end being the larger. That, the larger granules represent 

 the distal end is shown very well in the metaphase figures E, F, 

 G, and H. A fm-ther indication that these larger granules are 

 at the distal end is their behavior toward each other. In all of 

 the cells studied which were at stages corresponding to cells 

 A and B, these large granules stood widely apart from each other. 

 The example in cell A shows this especially well. It would 

 hardly be supposed that the proximal ends of a pair, being the 

 first to conjugate, would behave in this manner, while the distal 

 ends might easily fail of complete pairing. Now, since it is 

 possible to determine which end is proximal and which distal, 

 it is also possible, I believe, to trace the entire series of changes 

 into the metaphase. In cell A the primary spht is visible at the 

 distal end- (at the right in the figure) of this chromosome, but 



