1 91 8.] Eryihrism in Birds' Eggs. 73 



Pellorneum lay non-erytliristic eggs, Pellorneuni ignotum and 

 its subspecies lay quite red eggs. So true is this that I may 

 point out that P. i. cinnamomeum until very recently was 

 placed in another germs, Dnjmocataphus, and it was a know- 

 ledge of its curiously erythristic eggs which enabled me to 

 show Col. H. Harington where it should be placed. 



From the Prinia inornata exhibit quite a different line 

 of reasoning may be worked out, aud possibly we are here 

 given a clue to one of the causes of erythrism. The breeding- 

 ground of Prinia, generally speaking, is dry grass or scrul)- 

 covered land, or mixed low bush and grass country, free 

 from water and above flood-level. P. i. blanfordij however, 

 which lays the red eggs, is to be found breeding almost 

 invariably in heavy grass in marshes, swamps, or flooded 

 land. Is there any connection between erythrism and 

 humidity ? 



So far my exhibit has dealt with forms of erythrism for 

 which we can advance no reason or cause, or, as in the last 

 case, can offer mere conjecture or suggest a line lor further 

 research. Erythrism can, however, be carried somewhat 

 further than this, for there is a form of it which we can 

 explain as the direct result of evolution with a definite cause. 

 My last and most interesting exhibit gives examples of this. 



First, the large eggs shown at the top of the box consist 

 of two clutches of eggs of the Yellow-wattled Plover, 

 Sarciop/iorus malabaricus ; one of these is normal, the 

 second a very beautiful type of erythrism. In this par- 

 ticular instance there are good reasons for the evolution of 

 a red egg, and consequently it is not confined to a single 

 odd clutch here and there, but is found in very numerous 

 instances within a certain area. The probable solution 

 of this case is due to the researches of Mr. J. Stuart of 

 Travancore, who has spent much time and labour in its 

 elucidation. It appears that in the south-west of India, 

 near the coast of Travancore, there is a belt of country 

 where this Plover is resident in considerable numbers, 

 augmented in the breeding-season by a good many more 



