248 BIOLOGY: GENERAL AND MEDICAL 



make out that a particular feature showing itself in either parent 

 may: 



A. Present itself also in the offspring: 



1. Dominant, wholly replacing the corresponding but 

 divergent feature seen in the other parent. 



2. Blended, this particular feature in the offspring being 

 intermediate in character between that exhibited in 

 the two parents. 



3. In mosaic form, in certain cells the paternal, in others 

 the maternal feature being dominant. 



4. Blended and excessive, the features being more pro- 

 nounced than in either parent. 



B. Be unrecognizable in the offspring: 



1. Recessive, and replaced by the corresponding feature 

 derived from the other parent, but as such latent, 

 capable of reappearing in later generations. 



2. Absent, wholly wanting in subsequent generations, the 

 absence being due either: 



a. To casting out of an inherited condition, or 



b. To the feature seen in the parent being an ac- 

 quirement and not an inheritance. 



" On the other hand, considering the individual, we note that as 

 regards any particular feature or group of features there may be: 



A. Normal Inheritance. The offspring not being in this respect 

 advanced beyond either parent, but at the same time not fallen 

 behind. 



B. Progressive Inheritance. The offspring being advanced 

 beyond the more advanced of the two parents and exhibiting 

 either: 



1. Excessive development of the condition or conditions 

 already observable in one or both parents, or 



2. Spontaneous variations (mutation) ; i.e., the appearance 

 of conditions not previously noted in either parent or 

 either parental stock. 



C. Retrogressive or Reversionary Inheritance. The offspring 

 reverting as regards any feature or group of features to a lower 

 stage in the phylogeny of the species. 



D. Non-inheritance. Apparent or actual. 



"From this analysis one thing at least is obvious, namely, that 

 the biophores derived from either parent are liable to retain their 

 identity for some generations. Or, to be more accurate, that 

 qualities conveyed by the parental biophores may be retained, 

 even if in a recessive or latent condition. 



"That, indeed, is clearly proved by the Mendelian studies on 

 hybridization: after six generations or more with self-fertilization 

 the hybrid can give origin to plants exhibiting the pure features 

 of either the dominant or recessive ancestor. Conjugation cannot, 

 therefore, be of the nature of a chemical union of the biophores 

 from the two sources with resultant formation of a new biophoric 

 substance. ^ On the other hand, we cannot conclude that all the 

 separate biophores contributed by and representing each ancestor 

 are potentially present in the fertilized ovum. This would 



