MULTIPLE CHROMOSOMES 529 



smaller is always recognizable by its minor size and also by its 

 variability of form. In this Matter respect it may appear as a fully 

 formed ring, or it may show varying degrees of separation at one 

 of the polar angles, resulting in a large V-shaped structure. 

 Any one individual animal however shows either a ring or a V 

 and this does not suffer variation in any cells. 



In class 5, represented by seven individuals, we encounter 

 again the number ten as in class 3, but it is constituted in a dif- 

 ferent manner. The absence of the hexad multiple is at once 

 apparent, for the accessory chromosome is free and occupies a 

 characteristic polar position. Its sometimes associated tetrad 

 appears among the seven chromosomes of this type and there 

 are in addition, two large rings as in cells of class 4. So far as 

 can be seen, these two elements are as directly comparable with 

 the corresponding two of the preceding class as are similar struc- 

 tures within either of these classes. 



To the complexity resulting from combinations of separate 

 elements into multiples, thus reducmg the number of independ- 

 ent structures, there is added the opposite condition of a super- 

 numerary chromosome in the animal found in class 5-a. This 

 has a complex similar in its composition to the ones in class five 

 to which is added a small, extra element with the usual charac- 

 teristics of the supernumerary chromosomes. For the third 

 time there appears the number eleven, but its make-up is different 

 from the complexes of either class 2 or class 6. 



The number eleven reappears in cells of the six individuals in 

 class 6, but once again there is lacking the hexad multiple char- 

 acteristic of classes 2, 3, and 4. Nine ordinary tetrads, a free 

 accessory chromosome and one large Stenobothrus ring make up 

 the complex in this group. In place of the smaller ring, or V, 

 of classes 4 and 5 there are present two rod-shaped chromosomes 

 of corresponding size. The large ring occurs in five of the six 

 individuals and is directly comparable to the element faUing in 

 the same place in complexes of classes 3, 4 and 5. The sixth 

 specimen of this group has, in place of the ring, a large V of the 

 same construction as the smaller octad in class 4. This is the 

 only individual in which the larger tetrads were not imited at 



