GENERAI, TOPICS IN INHERITANCE. 



Now, by hypothesis we should expect a difference in inheritance in these 

 characteristics as indicated below : 



Expected nou-Mendelian. 





Expected Mendelian. 



1. Pea and rose comb vs. single comb. 



2. Muff and beard vs. plain head. 



3. Long tail vs. normal. 



4. Extra toe vs. normal. 



5. Melanic feet and beak vs. willow or 



yellow. 



1. High nostril vs. low. 



2. Cerebral hernia vs. normal. 



3. Taillessness vs. normal tail. 



4. Albinism in plumage vs. pigment. 



5. Absence of wing bar vs. presence. 



6. Absence of shafting vs. presence. 



Of the five cases where, on de Vries's theory, we should expect non-Men- 

 delian results, No. 4 is apparently not Mendelian, No. 5 gives often a 

 mixture of characters, Nos. i and 2 apparently give true Mendelian domi- 

 nance and recessiveness, No. 3 is still doubtful. Of the six cases in which 

 a Mendelian inheritance is looked for, we certainly find it in three cases and 

 less certainly in the others. On the whole, there is a slight but not a striking 

 difference in transmission between the two sets of characteristics, and I can 

 only conclude that for poultry, so far as I can see at present, de Vries's/ 

 formula does not hold universally. 



INHERITANCE OF POSITIVE VS. NEGATIVE VARIETAI, CHARACTERISTICS. 



According to de Vries, when an individual having a certain characteristic 

 patent is crossed with one in which it is latent the patent characteristic is 

 dominant, the latent recessive. Do results with poultry confirm this law ? 



In the following table the patent characteristic is given in the left-hand 

 column and the dominant characteristic in italics : 



Patent. 



Latent. 



Nasal process of premaxillary, narrow 



nostril. 

 Closure of cerebrum completed ; plain 



head. 

 Crest ; black crest feathers . 



4. Complete development of the feather . 



5. Tail 



6. Pigmented plumage 



7. Red wing bar 



8. Shafting 



High nostril. 



Failure of cerebrum to close ; cerebral 



hernia. 



Smooth head ; white crest feathers. 

 Interrupted development of the feather ; 



silky feather. 

 Taillessness. 

 Albinism in plumage. 

 Uniformly colored wing. 

 Plain feather. 



Of the foregoing eight characters, seven clearly follow the law that patent 

 characteristics dominate over latent. No. 6 is a clear exception, for since 

 all the wild Gallinae are deeply pigmented birds it can hardly be doubted 

 that white is a negative variation in which color is latent. However, the 

 exception (No. 6) is not universal, for white plumage does not always domi- 



