444 Tricotylous Races. 



Proportion of tricotyls in percentages 10 20 30 40 50 60 70 80 90 



Number of tricotylous individuals — — — 1 6111-ilO 1 



Number of atavistic individuals 1 4 3 10 1111 6 



Calculated for the whole progeny 1 4 4 19 27 32 21 1 



The average value for the tricotyls is 72^0 and of the 

 atavists 60%, which latter figure is of itself high enough 

 for an intermediate race. The last row was obtained 

 l\v means of a correction of the values of the tricotyls, 

 since too small a number of these had been cultivated in 

 com])arison with the atavists. The whole curve is ob- 

 viously monomorphic although much flattened. 



A curve with such a great amplitude indicates a cor- 

 responding high variability and therefore also a consider- 

 able susceptibility to external influences, as we have found 

 in several instances to be the case with intermediate races. 



To this great amplitude also the fact is due that se- 

 lection, however stringent, never cjuite eliminates the 

 lower values. Even when the apex of the curve is be- 

 tween 60 and 70%, values as low as 25% may still 

 occur. In such cases the curve has a ''sweep" to the 

 atavistic side, and thus differs most conspicuously from 

 the curves of the half race, the shape of which might be 

 considered as its mirrored image ; but as I shall come 

 back to this point when I deal with syncotylous races, 

 I shall not give any instances now. 



§ 7. PARTIAL VARIABILITY OF TRICOTYLY. 



In experiments with tricotylous races the hereditary 

 capacity or value is, as we have seen, the main character 

 subjected to selection. This term indicates the number 

 of tricotylous seedlings in the harvest. The seeds of 

 each individual are saved and sown separately, and then 

 recorded after germination. Whether the individual it- 



