548 Mr. C. F. ]M. Swynnerton on 



deterrent in themselves) or for protection from legitimate 

 attack. Or the model round which the others, so to speak, 

 centre, may be multiple — consisting of several related species 

 of nearly the same appearance. It is in this sense that I 

 suggest below that the Tits' eggs may have been the model 

 for one association and those of the Picarise for another. 



An illustration will be useful. My cat was once com- 

 pletely nauseated by a Drongo I gave him, and thereafter 

 " placed " Drongo very lov/ indeed. One day I offered him, 

 first a Drongo, then, in turn, a male Cuckoo-Shrike [Campe- 

 phaga nigra), a. Black Flycatcher [Bradyornis ater), and a 

 Black Tit {Paj'us niger). I laid each on its back on the 

 ground, in which position all, the first three especially, 

 resembled the Drongo. The cat refused the Drongo, and 

 thereafter refused even to come forward and smell any of 

 the others. I now turned each one in turn on to its breast. 

 Each was still neglected till I came to the Tit. This the cat 

 at once came forward to, the white of the upper wing-coverts 

 obviously showing him that it was no Drongo. I now 

 carried out a preference experiment with meat-scraps from 

 each bird. I found that the Flycatcher was placed nearly 

 or quite as low as the Drongo, the Cuckoo-Shrike far 

 higher, yet by no means amongst the species that are 

 accepted to repletion-point. Thus (if it be a case of mimicry 

 — as field-observation suggests), the association, as we find 

 it at Chirinda, consists of: (1) two species of Drongo, 

 abundant and low-grade, constituting the " modeP''; (2) a 

 Flycatcher, which, being as low-grade as the Drongos, yet 

 much scarcer, might be regarded as having mimicked them 

 for the sake of greater notoriety ; (3) a male Cuckoo-Shrike, 

 scarcer, also higher in grade, though still to some extent 

 deterrent, and probably, therefore, a mimic in virtue of its 

 greater liability to both legitimate and mistaken attacks. 



Theory. 



1. The Defences of Eggs. — The principle of alternative 

 defences and complementation that underlies Wallace's 

 explanation holds good. Some eggs are guarded by more 



