MULTIPLE CHROMOSOMES 569 



These are represented very exactly in Robertson's ('16) figures 

 174, 179, 180 and 182, and the achromatic break is considered the 

 point of union between tetrads. I believe that the weight of 

 e\ddence supports this interpretation: that these are indeed po- 

 tentially multiple chromosomes, but at the same time I feel 

 that there is no justification for the belief that this form of chro- 

 mosome is the result of the union of two tetrads of such shapes 

 that this configuration results. My evidence for this is that just 

 such shapes occur in full complexes of twenty-three chromosomes, 

 of both telomitic and atelomitic type. They are found in many 

 species and have been figured by Sutton, Granata, and myself. 

 As I have pointed out, the two rings lie in planes perpendicular 

 to each other and their origin is easily conceived if the chromo- 

 some is constituted of four parallel rods. A similar conception 

 appears in the interpretations of the other two authors cited. 

 The same difference between double rings of the telomitic and 

 atelomitic types holds as in the case of simpler annular chromo- 

 somes of the two types, for the fiber attachment is persistent 

 and determines the position of the chromosome on the spindle. 

 Therefore such structures are very much alike in Trimerotropis 

 and Stenobothrus and are so placed on the first spermatocyte 

 spindle that the ring to which the fiber attaches lies parallel 

 with its axis, while in forms with telomitic chromosomes only, 

 such as Hippiscus, Tropidolophus, Brachystola and others, the 

 ring to whose 'lugs' the fibers attach lies in the equatorial plate 

 Such differences are however entirely independent of simple or 

 multiple composition of the diploid chromosomes. 



Finally I consider them valueless as criteria of multiple con- 

 stitution, because in Chloealtis, a genus nearly related to 

 Chorthippus, the same numerical and size relations obtain, and 

 there are no double rings to suggest preservation of chromosome 

 forms such as are found in more widely removed genera. So far 

 as the form of the chromosomes is concerned, the conditions in 

 the Tryxahne, Chloealtis, are much more nearly hke those in 

 H. viridis, of the Acridiinae, than they are in Chorthippus, a 

 very nearly related genus. 



