'892-J Elliot on Hybridism. l6l 



confusion thereby. B}^ many persons, who have not appreciated 

 the fact of this existence of hybridism, crosses arising from the 

 interbreeding of distinct species have been described from time 

 to time as new species, although to those more familiar with the 

 subject the evidence of their descent, shown in their style of color- 

 ation, and often in the outline and structure of the bill, is mani- 

 fested almost at a glance. 



Among ornithologists, as a rule, there seems to have existed 

 a strange reluctance to acknowledge this condition of hybridism, 

 the reason for which would be very difficult to explain, save 

 where in some instances it might conflict with preconceived 

 opinions or theories entertained by various authors. One of the 

 most, if not the most, remarkable conditions of hybridism known 

 to us, is that produced by the crossing of Colaptes cafer 

 and C ani-atus^ the offspring of which has been known in our 

 literature as C. kybridtis, and the evidence of which has been 

 witnessed over a vast extent of North America ; but even in this 

 case it has not been ascertained that the hybrids have been fertile 

 to any very great degree, although the information gathered 

 would seem to foretell the gradual curtailment of the range of C. 

 cafer as tlie dominant form, C. mu-atus, intrudes itself farther 

 and forther upon its domain. 



Perhaps the most numerous examples of intercrossing have 

 been obtained from the families of the Pliasianidie and Anatidie, 

 and species of both of these are known to interbreed more or less 

 readily under the conditions pertaining to domestication. But 

 even under such circumstances, when the physical conditions of 

 the birds have attained a most perfect development, and their 

 passions JKive been excited by stimulating food to the highest 

 degree, fertility rarely extends beyond the second generation 

 among the hybrids breeding inter se. Prof. Newton (P. Z. S. 

 iS6o, p. 338) instances a case that came under his own observa- 

 tion, where a pair of hybrids, the result of a cross between Anas 

 boschas and Dajila acjita, interbred, as he believed, near a 

 pond in his park, and produced four young, two males and two 

 females. During the next breeding season these birds were 

 closely watched. His observations led him to regard them as 

 infertile, and his belief was shown to be well founded, when he 

 dissected them after death, proving that in this case ability to re- 

 produce their kind did not extend to the second generation. 



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