190 Retrograde Varieties 



yielding new, and very often, valuable varieties. 

 But it is manifest that this form of variation 

 is of quite another nature from the variations 

 of pure races. Many hybrid varieties are quite 

 constant, and remain true to their type if no 

 further crosses are made ; many others are arti- 

 ficially propagated only in a vegetative way, 

 and for this reason are always found true. 

 Hybrid varieties as a rule were formerly con- 

 fused with pure varieties, and in many in- 

 stances our knowledge as to their origin is quite 

 insufficient for sharp distinctions. To every 

 student of nature it is obvious, that crossing 

 and pure variability are wholly distinct groups 

 of phenomena, which should never be treated 

 under the same head, or under the same name. 

 Leaving aside polymorphy, we may now dis- 

 cuss those cases of variability, in which the 

 changes themselves, and not only their final 

 results play a part. Of such changes two types 

 exist. First, the ever-recurring variability, 

 never absent in any large group of individuals, 

 and determining the differences which are al- 

 ways to be seen between parents and their 

 children, or between the children themselves. 

 This type is commonly called '^ individual 

 variabilitv " and since this term also has still 

 other meanings, it has of late become customary 

 to use instead the term ^' fluctuating varia- 



