1917-] Letters, Extracts, and Notes;. 271 



ornithologists being necessarily less acquainted with the 

 details of the theories of mimicry and warning colours than 

 are entomologists, I ought to include in my paper a discussion 

 of the principles involved ; and I think it was perhaps well 

 to do this even if I suggested mimicry merely " as a possibly 

 useful line of contributory explanation " (p. 554). But I 

 freely admit that I was in any case more inclined to believe 

 in the probable occurrence of true mimicry in eggs and 

 mouths at the time I commenced to write the paper than I 

 am now. 



The following corrections should be made : — 



Page 5oo, line 30. For " few " and " elements " read " far " and 



" element." 

 " indicated " read " vindicated." 

 "probable " read "provable." 

 " those " read " three." 

 "chitinous " read " chitinless." 

 "in many cases " read " in any case." 

 "selection " read " selective." Also on p. 571, 



]. 8. 

 Geochelidon read Gelochelidon. 

 " hence " read " have " ; omit " have " in next 



line, 

 "forms " re.ad "form." 

 " as " read " or." 

 Fig. 14 is Ilyphantornis jamesotii, a Dicruroid form of the 



egg, not Pycnonotus layardi. 



As for the prohahilitrj of the view (p. 558^ 1. 11) that the 

 influence exercised by parasitic birds may have been great, 

 I need only say that I find it difficult now to regard it as 

 a coincidence that the order which shows the greatest 

 diversity in the coloration of its eggs should also be the one 

 that is most liable to victimization by Cuckoos, and that my 

 experiments iii the substitution of eggs have convinced me 

 that the need for the baffling of Cuckoos, leading to the 

 encouragement of variability within the species, may well 

 have been the primary, if indirect, factor in the production 

 of that diversity as well as an important contributor to the 



