ASSOCIATION OF CHROMOSOMES IN DIPTERA 259 



9. In certain respects the pairing phenomena were found to 

 present a striking similarity to synaptic phenomena. They 

 give an actual demonstration of a side by side approximation 

 of corresponding chromosomes. 



These facts lend strong support to the conclusions: 



1. That the paired arrangement of chromosomes is not due 

 to a random assorting process, but is selective to the highest 

 degree. 



2. That each maternal chromosome becomes associated with 

 a definite, similar paternal chromosome and with no other. 



3. That chromosome pairing is dependent upon the quali- 

 tative nature of the chromosomes, — and more specifically upon 

 a qualitative (physico-chemical) similarity between associating 

 members. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 21, NO, 2 



