The progress of Genetics since tlie rediscovery of Mendel's papers. 397 



Similar phenomena of partial coupling" exist in regard to the 

 sterility of anthers in the Sweet Pea and the absence of colour in 

 the axil; and also, in the same species, with reg'ard to the develop- 

 ment of the hooded standard and certain colours, but the lormulae 

 for these cases have not yet been determined. 



Miscellaneous unconformable Cases. 



Of such cases we at present know very little for certain. Occa- 

 sionally we meet with phenomena which appear to indicate an imper- 

 fection of segregation. For instance at Messrs. Sutton's I have 

 seen a family of Primula Sinensis, in which many intermediates 

 between the palm and fern leaved condition occurred. There may 

 no doubt have been imperfections in the dominance of the palm type. 

 The numbers were inadequate to justify an analysis. Even from 

 such a family the fernleaved members no doubt breed true. 



Castle adheres to the view that pied forms indicate an imper- 

 fection of segregation. The propriety of this view becomes less clear 

 in the light of modern evidence proving the existence of determiners 

 for pattern. 



Among colours C u é n o t ' s facts indicate that something abnormal 

 occurs in the segregation of yellow from the black-containing colours 

 in mice, and so far as I am aware, nothing precisely comparable has 

 been met with elsewhere. 



Castle (18) has found that the lop-eared character in rabbits 

 does not segregate from the normal ear, but that the intermediate 

 breeds true. Mr. Staples-Browne tells me that in Pigeons the 

 l)eculiar many-quilled tail of the Fan-tail (with upwards of 30 quills) 

 has not hitherto in his experiments re-appeared in Fo from crosses 

 with the original 12-quilled type. Fj is a blendform, and though Fg 

 contains birds with the 12 quills of the original type, none have the 

 fully developed "fan" with its 30, or more, quills. 



He found (91) also that the webbed condition of the toes is 

 recessive to the normal foot. But in F^ none of the récessives were 

 so much webbed as the original webbed bird, and much intergrading 

 was observed. 



A good many cases are known where a particular parental type 

 does not re-appear in F^. In other cases a parental type recurs, but 

 very rarely. Such rarity we now ascribe with confidence to the 

 existence of a great number of factors capable of concealing the type 

 in question, and without doubt in very large series of individuals the 



