367 



anterior portions of the brain are entirely contained in this tuberosif y, 

 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 intertnaxillary boues. 



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 betweeu 

 it and the tuberosity is eonstrieted, the brain necessarily assumes 

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



This very extraordinary structure, which is well developed eren 

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

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

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

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

 fowls are remarkably stupid, whereas their instiucts do not appear 

 to diflfer in the slightest degree from those of the other uon-incu- 

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

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

 not exist. 



Palias, who also notices the peculiarity, erroneously attributes it 



