Huxley, A "Disharmony" in the Reproductive Habits of the Wild Duck. 621 



auch hier intermediare Vererbung herrscht, wie bei alien Art- und 

 Varietatenkreuzungen. 



So sind auch die neuesten Versuche, die intermediare Vererbung 

 mendelistisch aufzulosen, inissgliickt, haben ihre Existenz vielmehr 

 an einem grofien Material von neuem bewiesen. (Schluss folgt.) 



A "Disharmony" in the Reproductive Habits of the 



Wild Duck (Anas boschas, L.). 

 By Julian S. Huxley, Balliol College, Oxford. 



The following facts concerning the behaviour of the Mallard 

 afford a very striking and indeed surprising example, in a wild species 

 and under natural conditions, of what Metschnikoff has taught us 

 to call a Disharmony a lack of adaptation leading to harmful 

 results for the species; and, since these facts appear not to be widely 

 known, I venture to record them here. 



They are as follows: The Wild Duck is monogamous, and the 

 drake or Mallard, though as a rule he neither feeds the sitting 

 female nor helps to bring up the young, yet manifests considerable 

 attachment to his mate. During the time of incubation, the drakes 

 are usually said to take no interest in the ducks, and, congregating 

 into bands, to lead a lazy bachelor existence. This is only partially 

 true; the males do congregate in such bands, but only for part of 

 the time. At intervals the drake returns to the neighbourhood of 

 his sitting mate, stayng there often for hours together. This he will 

 do even if she has built at a long distance from the water. When 

 a duck is put up off her nest, her drake will often be seen to fly 

 up and join her in the air. 



So far all is normal and decent. Now comes the disharmony. 

 When a duck flies off her nest, it is often not only her own mate 

 that flies up to join her; other drakes (I believe including those 

 that are resting near their own ducks as well as the temporary 

 bachelors) may fly up from all sides, and set off in pursuit. In April 

 it is a very common sight to see from two to ten drakes thus 

 chasing a single duck, and occasionally there will be many more. She 

 doubles and turns, but, being smaller in size than the drakes, can 

 never escape from them by speed alone. How then do these 

 polyandrous pursuits end? Sometimes the drakes get tired of the 

 chase while still in mid-air, and one by one drop down. If this does 

 not happen, and the duck has at length to come down on the water, 

 there may still be no particular sequal - - only a good deal of excited 

 quacking and swimming about and mild fighting - - the real husband 

 being finally left alone with his mate. But sometimes, especially 

 when the drakes are very numerous, they regularly mob the single 



