Mr. Tegetmeier on the Skulls of Polish Fowls. 483 



being protected from external injury solely by the feathers of the 

 crest and the integuments ; the posterior portions are situated, as 



No. 1.— Skull of Crested Hen (var. Golden-spangled Polish), showing sphe- 

 rical tuberosity and deficient intermaxillary bones. 



No. 2. — Longitudinal vertical section of the skull of a Crested Cock (var. Silver- 

 spangled Polish), showing the shape of the cavity containing the encephalon. 



usual, in the cavity of the cranium : as the communication between 

 it and the tuberosity is constricted, the brain necessarily assumes 

 the form of an hour-glass, the anterior being the larger portion. 



This very extraordinary structure, which is well developed even 

 before the escape of the chick from the shell, was noticed by Peter 

 Borelli in 1656, and again described with many errors by Blumen- 

 bach in ' De Nisus formativi Aberrationibus,' 1813. Blumenbach 

 states that it is confined to the females, which is incorrect ; that the 

 fowls are remarkably stupid, whereas their instincts do not appear 

 to differ in the slightest degree from those of the other non-incu- 

 bating varieties of domestic fowl ; and lastly, that the tuberosity is 

 caused by a tight constriction of the integuments, which however does 

 not exist. 



Pallas, who also notices the peculiarit}^ erroneously attributes it 

 to a cross with the Numida meleagris ; and the description of a 



31* 



