254 Retrograde Varieties 



their qualities from both parents ; for each sin- 

 gle mark they possess at least two units. Prac- 

 tically but not absolutely equal, these two op- 

 ponents always work together and give to the 

 offspring a likeness to both parents. No un- 

 paired qualities occur in normal offspring ; these 

 constitute the essential features of the hybrids 

 of species and are at the same time the cause of 

 their wide deviations from the ordinary rules. 



Turning now to the varieties, we likewise 

 need discuss their differentiating marks only. 

 In the negative types, these consist of the ap- 

 parent loss of some quality which was active in 

 the species. But it was pointed out in our last 

 lecture that such a change is an apparent loss. 

 On a closer inquiry we are led to the assumption 

 of a latent or dormant state. The presumably 

 lost characters have not absolutely, or at least 

 not permanently disappeared. They show 

 their presence by some slight indication of the 

 quality they represent, or by occasional revers- 

 ions. They are not wanting, but only latent. 



Basing our discussion concerning the process 

 of crossing on this conception, and still limiting 

 the discussion to one differentiating mark, we 

 come to the inference, that this mark is present 

 and active in the species, and present but dor- 

 mant in the variety. Thus it is present in both, 

 and as all other characters not differentiating 



