72 Mr. E. C. Stuart Bal<er on [Ibis, 



Pellorneum ignotum, Prinia socialis, and Ruticilla frontalis, 

 ■which all lay truly erytliristic eggs, whereas the majority of 

 the remaining species of the same genera lay eggs of quite 

 different coloration. To show the contrast, the erythristic 

 and non-erythristic eggs are shown together. 



Finally, normal erythrism may be shown in the eggs of 

 one subspecies of a species, all the rest of which show none. 

 This is, I think, a rare form of erythrism, but occurs now 

 and then. The exhibit shown is a very beautiful example, 

 the eggs of Piinia inornata blanfordi being fine red eggs, 

 whilst P. i. inornata, P. i. extensicauda, P. i. burmanica^ and 

 P. i.jerdoni all lay equally beautiful, but bright blue, eggs. 



The above embraces examples of the facts which are 

 already known to all oologists, though perhaps they have 

 not yet been enumerated in a similar manner; wheu we 

 advance beyond these facts we seem at once to enter the 

 second class, that of abnormal erythrism. Here, however, 

 we enter so wide a field that I have really not attempted to 

 show anything beyond a couple of species, Corvus splendens 

 and Tiinelia pileata, in which erythrism is very rare, and two 

 other species, Dendrocitta rufa and Orthotomus atriguluris, 

 in wliich it is so common that it becomes an almost normal 

 l)hase of coloration. Exceptionally rare and beautiful 

 examples of erythrism are being shown by many of our 

 members to-night, and will more than serve as illustrations 

 of abnormal coloration. 



From the remarks I have made and the exhibits shown, 

 1 hope some deductions may be drawn. Thus it may suffice 

 to maintain that if coloration and other characteristics of eggs 

 form any guide to systematic classification, erythrism, or its 

 absence, should be one type of coloration worthy of careful 

 consideration. As regards families, it shows that a non- 

 erythristic egg cannot belong to any bird which should be 

 placed amongst the Bulbuls. Again, no non-erythristic egg 

 can be laid by any bird entitled to a place in the Tribura 

 group of genera. Lower down the grades we find that, 

 whereas all the other known species and subspecies of 



