TESTES OF GUINEA-CHICKEN HYBRIDS 49 



carried out on hybrid pigeons from 1897 to 1900; namely, that 



(p. 46) 



in hybrids it may be supposed that in the ordinary cells of the body, the 

 chromosomes from the paternal and the maternal species lie side by side 

 ana carry on the customary functions of the cells but when it comes to an 

 actual fusion of chromosomes to form the bivalent type necessary for 

 reduction, the incompatibility of the two different plasmas renders the 

 union incomplete or prevents it entirely. 



It may be of some interest in connection with the present mem- 

 orial volume to record the fact that practically all of this earlier 

 work on hybrid pigeons was done on material supplied by 

 Professor Whitman himself. He was particularly curious about 

 the preponderance of males among his hybrids, and was much 

 interested in the interpretation expressed in my doctoral thesis 

 of 1900 to the effect that the refusal of the chromosomes of hybrids 

 to unite in the first spermatocyte indicated that synapsis normally 

 was a fusion of maternal with paternal chromosomes, and that, 

 granting this to be true, in fertile hybrids in the segregation of the 

 chromosomes after synapsis we find a plausible reason for returns 

 in the third generation to grandparental characteristics. Since 

 this paper has had but a limited circulation it may not be amiss 

 to restate briefly my conclusions at that time regarding this 

 point. In a paper in 1899^ I had already pointed out the fact, 

 illustrating with a diagram, that when white ring-doves and brown 

 ring-doves are cross-mated and their offspring interbred, there is 

 frequently a return in color in the third generation to the grand- 

 parental types. This phenomenon we now recognize at once as 

 Mendelian but at that time Mendelism had not yet been redis- 

 covered. In my thesis'* of the next year I restated these facts of 

 my 1899 paper a little more explicitly as follows (p. 35-36) : 



Offspring of the common ring dove when crossed with the white ring 

 dove are brown in color. One member of the resulting pair is frequently 

 a few shades lighter in color than the other. In the next or third genera- 

 tion there is generally a return to the original colors of the grandparents; 

 one of the young is white, the other brown. Occasionahy both of the 

 young are brown or, less frequently, both white. There is a marked 

 tendency for the white ones to be female and the brown ones male. 



5 Zoological Bulletin, vol. 2, no. 5; 1899. 

 * Loc. cit. 



