1918.] Erythrism m Birds' Eggs. 71 



genera and forty species of Indian Bulbuls, and tliose who 

 know tlie African species will see that many of them could be 

 duplicated by these and even substituted for them without 

 fear of detection. 



Sharpe, in his Hand-list, includes Oates's Brachypodina 

 in the Pycnonotidce together with the genera ^githina, 

 jEthorhynchus, Chloropsis, and Irena. The eggs of these 

 four genera would at once lead us to infer that they belong 

 to quite different groups, and a careful study of the birds, 

 to my mind, confirms what the eggs first tell us. Irena is 

 probably a Thrush, to be placed somewhere near the genus 

 Cochoa, whilst the other three genera must be placed with 

 other Timeleine forms or else constitute a group by them- 

 selves. 



Next to families and subfamilies, and before dealing with 

 single genera, it is necessary to consider certain groups of 

 genera which cannot be excluded from families containing 

 many others, yet which are remarkable for the close re- 

 semblance between their eggs, shown, in so far as we are 

 concerned this evening, by their erythrism. For this 

 })urpose I show three small boxes containing eggs of the 

 Sylviine genera Urosphena, Horeites, Neornis, Horurnis, and 

 Cettia. So closely are these allied that many naturalists 

 have merged two or more of them into one. This com- 

 bination of the genera seems to be sound the more we 

 study the birds, and the wonderful ervthristic character 

 of the eggs would certainly seem to endorse it. 



After groups of genera we naturally come to isolated 

 genera, all the species of which show erythrism well defined 

 though varying somewhat in degree. Such genera are 

 exemplified to-night by Chloropsis, Pyciorhis, and Piprisoma, 

 each with several species, but such examples may be added 

 to almost ad in/iuiium. 



To generic erythrism naturally succeeds specific erythrism, 

 and we find that many genera contain species some of which 

 lay erythristic eggs, whilst others lay eggs in wdiich there 

 is no trace of red. To such genera belong the species 



