CROSSING OVER AND CHROMOSOMES 109 



In the second division of this chromosome the longer 

 thread separates from the shorter one— the second is 

 therefore rednctional. It is evident, especially from this 



\i b 



d 



f 



g 



h 



d 



f 



h 



a 



d 



a 



Fig. 48. — A pair of chromosomes "B" in eonjugation. 1; thr same pair in con,iu?a- 

 tion in another indi\'idual in which one chromosoine is shorter than the other, 2; same 

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



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

 indication that the division of the chromosome is neces- 

 sarily different from what it is when there is no such 

 crossing. What is more important is that the crossed 



