Family ARDEIDAE. 

 (Plates 118—121). 



The characteristic points of difference between eggs of Ardea 

 purpurea L. and A. cinerca L. consist in tiie facts that: 



r in A. purpurea a thin layer of lime is spread, as is it were 

 lilvc a continuous veil, over the uppermost pigment layer, while in 

 A. cinerca numerous separate particles of lime form so many scat- 

 tered white specks; 



2° the pigment layer mentioned under 1°, superposed in both 

 species on the deeper layers — coloured blue by oocyanin — , also 

 contains a green pigment (biliprasin) ') which occurs as a rule in 

 a much stronger measure in A. cinerca than in A. purpurea. 



For c/ncrcfl-eggs that are pigmented green in a weaker degree, 

 as well as for purpurea-eggs that are coloured green in a stronger 

 degree than is usually the case, the distinguishing feature mentioned 

 under 1° obtains undiminished. 



As it appeared that the true nature of the large white and yel- 

 lowish spots which occur so frequently, e. g. on eggs of Ardca- 

 species, had never been examined before, Mr. J. H. Aberson, 

 Instructor in Chemistry at the State High Agricultural, Horticultural 



') Found by Krukenberg in the eggshells of, among others, Corvinae, Turdinac, 

 and Ardcinac. (See his „Farbstoffe der Vogeleierschalen", in: Verhandl. der 

 phys. nicd. Gcsellsch. N. F. Bd. XVII, p. 117). 



