BUBONIDAE — STRIGIDAE. 



The eggshell is plain ] ) white, although not always of an equally 

 pure tint; or it inclines to cream colour. 2 ) When light shines 

 through them the eggshells of Strix are purest in tint; then follow 

 those of Athene and Syrnium; whilst those of Asio are yellowish. 

 The pores of the shell (when magnified 16 times) are plainly visible. 

 It appears to me that their number is smallest in Asio and largest 

 in Athene. 3 ) 



The genus Strix deviates oologically not only in shape but also 

 in composition of the uppermost layer of carbonate of lime, from 

 the other genera. 



As regards the mutual oological relation between the genera which 

 come into consideration here, this relation places Athene on a line 

 with Syrnium; it supports the union of otus and accipitrina in the 

 same genus (Asio) ; and makes Strix occupy an exceptional standpoint. 



Oological points of contact (in texture of the shell) with other 

 Families, agreeing with the results of phylogenetic investigations, 

 must, in so far as species of birds breeding in the Netherlands are 

 concerned, be sought for in Apus and Caprimulgus. 



*) Rey mentions two cases in which in his opinion markings caused by real 

 pigmentation were present: one in Syrnium aluco L., the second in Bubo 

 bubo L.; in the latter case the character of the markings, Rey says, reminded 

 him of that of eggs of Milvus korschun (S. G. Gmelin). See: „Ornith.Monats- 

 ber.", 1893, No. 4. and Rey'S „Eier der Vogel Mitteleuropa's, plate 122, fig. 3. 



2 ) Oates asserts that all newly laid eggs of Strigiformes are invariably plain 

 white, and that it is only after incubation that they acquire a cream coloured 

 or yellowish tint. (See, contra this assertion, what is stated in the present 

 publication respecting aluco and accipitrina). 



3 ) I do not understand how Oates could say that only the larger eggs 

 of the Strigiformes exhibit pores; in those of Athene noctua e.g., they are 

 plainly visible to the unaided eye. 



