On the Hybridising of Duels. 255 



and the Mallard is similar and of a greenish tint, while the 

 Spotbill and New Zealand Duck lay cream-coloured eggs. 

 Among the Spotbill -Mallard digens, and Pintail-Mallard- 

 Spotbill trigens the eggs (with one exception, those laid by 

 a dark trigen) are invariably greenish, but in the New 

 Zealand-Mallard-Spotbill trigens the eggs are without 

 exception cream-coloured. 



IV. Reversion. 



By " reversion " is meant resemblances shown in hybrids to 

 species other than their parents, these resemblances being 

 supposed to belong to an older and more archaic type. This 

 idea was proved by Darwin in the case of domestic Pigeons 

 which reverted to their wild ancestor, the Rock Dove, and 

 has also been established by several other observers in the 

 case of cultivated species of plants, but has never, so far as I 

 am aware, been proved true in the case of hybrids between 

 wild species. Bearing in mind how much further removed in 

 point of time pure wild species are from their common 

 ancestor as compared with domestic forms, and also the diffi- 

 culty experienced in crossing wild species, it is not surprising 

 that reversion in the case of wild forms should lack proof. 

 Nevertheless when it has been tried it has not been apparent, 

 and under the next heading I hope to bring forward some 

 cogent reasons to show that, if it exists, it must be considered 

 on very much broader lines than has hitherto been the case. 



As instances of resemblances to species, other than those 

 contained in their parentage, that have appeared in the course 

 of these experiments, we may note a resemblance, especially on 

 the underparts and in size, shown by a young female Pintail 

 trigen to a hen Gradwall ; also a close resemblance shown by 

 a New Zealand trigen Duck to a female Pintail, or, again, 

 the head of a New Zealand trigen Drake with markings 

 resembling some of those found on the Teal and Pintail, 

 and, lastly, flank feathers from a Pintail trigen of the 

 first generation, which are chestnut and practically indis- 

 tinguishable from those of a Wigeon. 1 



1 Examples of these, as well as of the hybrids, were exhibited at a meeting of 

 the Geological Society in March, 1905— P.Z.S., 1905, Yol. I., p. 147. 



