CROSSING OVEE AND CHEOMOSOMES 109 



In the second division of this chromosome the longer 

 thread separates from the shorter one— the second is 

 therefore reductional. It is evident, especially from this 



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h 



d 



a 



Fig. 48. — A pair of chromosomes "5" in conjugation, 1; the same pair in conjuga- 

 tion in another individual in which one chromosome is shorter than the other, 2; same 

 in a third individual, 3; later stage showing chiasma of threads, 4. (After Wenrich.) 



last example, that the crossing of the threads is not an 

 iadication that the division of the chromosome is neces- 

 sarily different from what it is when there is no such 

 crossing. Wliat is more important is that the crossed 



