48 Note 071 a Case of Linkage in Paratettix 



Hence out of 116 spermatozoa he must have produced : 

 45 A0, 17 B0, 17 A®, 37 JB0, 



or 34 cross-overs out of 116. When the mother was also heterozygous 

 for S certain classes of zygotes co\ild not be distinguished, and hence 

 only those classes are considered which enable us to measure the linkage 

 directly. Thus in mating 178 all the A6B9 and BOFd zygotes were 

 formed from non-cross-over spermatozoa, whilst A6A6 or AdFO would 

 have been due to crossing-over, 



TABLE I. 



Male doubly heterozygous. 



Totals 1421 335 



Out of 1421 spermatozoa produced by the doubly heterozygous males 

 335, or 23'6 °/^, were due to crossing-over. The cross-over value appears 

 to vary slightly with the pair of " multiple allelomorphs " concerned, 

 but the only variation which is probably significant is as follows. Where 

 one of the factors concerned is A, i.e. in matings 178, 180, and 187, the 

 cross-overs number 53 out of 180, giving a cross-over value of 29*4 + 2*3 °/^ , 



