220 CHARLES L. PARMENTER 



far as known, has been lost from one homologiie and joined to 

 the end of its mate. Another case is the transposition of a piece 

 of the II chromosome to the middle of the III chromosome. 

 He has exhibited definite cytological evidence (unpublished) 

 supporting a part of the above. This condition produces 

 homologues of unequal length which parallels the observations 

 in the germ cells of the Orthoptera and the apparent similar 

 condition in certain somatic homologues of Ambystoma. 



c. Constant relative size relations. In addition to verifying 

 Montgomery's ('01) and Sutton's ('02) observations of paired 

 homologous chromosomes of equal length in the germ cells, 

 Meek ('12), Robertson ('16), and Hance ('17 b, '18 a) confirm 

 Sutton's ('02) observation (based upon comparisons of camera- 

 lucida drawings of many spermatogonial cells and upon measure- 

 ments of early prophase tetrads) that the proportional difference 

 in size between any two pairs in one nucleus is practically the 

 same as that between the corresponding pairs in any other 

 nucleus. In Ambystoma tigrinum, as is seen in figures 33 to 

 37 and the table of percentages accompanying them, while 

 the relative lengths are not exactly the same in every cell, there 

 is in general a marked constancy of relative lengths. Were 

 Meves' and Delia Valle's measurements correct, the same would 

 probably appear there. 



d. Summary of measurements. The data here presented in 

 connection with measurements upon the chromosomes of Amby- 

 stoma tigrinum and Salamandra maculosa cannot well be inter- 

 preted as a confirmation of Meves' and Delia Valle's contention 

 that pairing of the chromosomes and a constant organization of 

 the chromosomes do not exist because: 1) Their data, on 

 account of errors inherent in the material, are too unreliable to 

 command confidence; 2) the differences in the lengths of the 

 chromosomes of Salamandra maculosa are too small to permit 

 one to deny or to affirm the existence of pairs, and, 3) it has 

 been shown that because of obvious foreshortenings, individually 

 mentioned above, which are unaccounted for in Meves' measure- 

 ments, there probably is a somewhat constant difference between 

 chromosomes 8 and 9 in eleven out of the twelve cells which he 



