109 [Vol. XXXV. 



and of the mouths of nestlings might have been acquired 

 to enable enemies to distinguish unacceptable eggs from 

 eggs for which they were sufficiently hungry at the 

 moment. 



It was possible, also, that the coloration of the groups 

 of eggs laid in holes (such as the white eggs laid by 

 Picarian birds, Martins, etc., and white eggs with pink spots 

 laid by Tits, Nuthatches, etc.) could not only be explained 

 by the already-accepted theories, but might be accounted 

 for by their distastefulness to enemies, each group 

 centring round a well-known and usually unacceptable 

 *^model.'^ This ''model" [i.e. the species or group 

 mimicked) might in one case be the Tits and in another 

 the Picarians. 



The possibility of " mimicry " in eggs must be treated 

 with the greatest caution, as pure coincidence in coloration 

 was so general a phenomenon; yet the polymorphic eggs 

 of certain Weavers might possibly, in Mr. Swynnerton's 

 opinion, be a case of mimicry. Many of the apparent 

 ''models,'"' which the eggs of these Weavers resembled so 

 closely, had been tested and found to be distasteful. The 

 eggs of Tits, some Warblers, and some Wagtails were also 

 unpalatable. The fact that Wagtails* eggs were sometimes 

 unacceptable suggested the possibility that the attacks of 

 enemies might even have contributed largely to mimicry in 

 Cuckoos'" eggs. 



Mr. S WYNNE RTON further exhibited enlarged coloured 

 drawings of the mouths of certain African nestling- birds, 

 illustrative of his theory that there was a strong warning 

 element in the coloration. Resemblances, probably in part 

 due to mimicry, were pointed out between the mouths 

 of unrelated nestlings, such as that of Hyphantornis 

 jamesoni and a Chrysococcyas found in the latter's nest ; and, 

 again, the resemblance between tbe mouths of CUoropeta 

 natalensis and such Warblers as Prinia mystacea (experi- 

 mentally found to be unpleasant) and Cisticola cimrascens. 



Dislike was shown for a nestling of Centropus burchelli 



