THE MORPHOLOGY OF THE CHROMOSOMES 



117 



of "telomitic" chromosomes. In Trillium delicate strands extend out 

 to the granules from the single arm of the telomitic chromosome and 

 from both arms of atelomitic ones (Fig. 63). A comparison of these 

 two types strongly suggests that in the former the attachment point is 

 truly terminal. What relation the delicate strands may bear to the 

 chromonemata is difficult to determine, especially since the chromosome 

 tends to stain very deeply on either side of the attachment region. 



The spindle-attachment region, then, is a well-differentiated feature 

 of the chromosome: it is a region specialized with reference to the meta- 

 phasic arrangement and anaphasic separation of double chromosomes 



\f 



-^ 



c / 



I 



Fig. 62. — Kinetic bodies at spindle-attachment regions. A, in GaJtonia microspore. 

 [After S. Nawaschin, 1927 (1913).] B, prophase in Najas major; C, anaphase in Crepis 

 palestina. (After Trankowsky, 1930a.) 





Fig. 63. — Submedian, subterminal, and apparently terminal spindle-attachment regions 



in Trillium grandiflorum. 



(p. 107) and is not to be confused with other achromatic regions or 

 "constrictions." That it persists through the interphase is indicated 

 in Impatiens, where it can be seen at all stages (Fig. 24, B). What is 

 known about the behavior of fragmented chromosomes (p. 317) suggests 

 that spindle-attachment regions cannot be formed anew. In all prob- 

 ability the regular occurrence of one such region in every chromosome 

 is due to the eventual loss of fragments without them because of their 

 inability to interact normally with the spindle, and to the irregular 

 behavior of any chromosome which happens to get an extra attachment 

 region through translocation. Hence the constancy and the regular 

 behavior of a group of chromosomes are directly dependent upon the 

 attachment regions. Whether or not a chromosome may fragment 



