326 Genetics of a Daphnia Hybrid during Parthenogenesis 



and their mean ratio was 10*4, practically the same as that of the hybrid 

 clone (101). 



A confirmation of the absence of segregation within the females of 

 the hybrid clone is the absence of bi- or multi-modality in the distribution 

 of the ratio values. Fig. 3 shows the distribution of each of the two 

 parental clones, and of generations 3 — 10 of the hybrid clone. The 

 latter shows no sign of multi-modality, though such would almost cer- 

 tainly manifest itself in the very early generations from the original 

 hybrid if segregation were taking place. Moreover, it is noticeable that 

 the extremes of the curves of all three clones are stretched out asym- 

 metrically towards the right (high ratio), and doubtless in the hybrid 

 clone this skewness is due to the same causes as in the parental clones — 

 i.e. not due to segregation but to non-genetic causes. 



Classes 

 Xc 

 H 

 RR 



1 55 1-65 1 75 1-85 1-95 205 215 225 235 245 255 265 275 2-86 295 305 315 325 335 345 3 55 3 65 TotslS 



2 12 28 54 57 65 43 7 5 2 1 276 



_ 4 9 13 17 15 10 6 1 75 



— 1 8 10 9 11 5 10 5 6 3 1— 69 



Means 



Standard Deviations Xc '169 



„ „ H -166 



RR -254 



Fig. 3. Distribution of the — ratio in females of clones Xc, H, and RR. For convenience 

 A 



of comparison, the curves are all constructed for 1000 individuals. The actual numbers 

 of individuals which provided the data are shown beneath the curves. 



Finally, the fact which was established above, that segregation does 

 not manifest itself among the hybrid male population implies that this 

 was absent also among the females which produced the males. 



