174 Journal of Comparative Neurology. 



This ratio for the black tern, Hydrochelidon, is 55.6; for the 

 domestic duck, 33.3 ; for the white peHcan, 36.9 ; for the wood 

 cock, 42.8 ; for the great horned owl, Bubo virginianus, 39.7 ; 

 for the golden eagle, 47.2. 



The eagle and the owl, both belonging to the Raptores 

 yet with conspicuous differences in powers of flight, differ by 

 7.5 per cent, in size of the cerebellum. There is a difference 

 of 8.2 per cent, in the volumes of the cerebrum in the opposite 

 direction, i. e. in favor of the owl. The domestic duck and 

 the pelican each possesses a very small cerebellum, while the 

 tern which is also a low type, but which has remarkable pow- 

 ers of flight, has a larger cerebellum than any of the birds tab- 

 ulated by Professor Turner. Upon inspection of his table 

 (Journal Com. Neurology, Vol. I, p. 84-85), it is apparent that 

 the swallow and other birds of strong wing-power have as a 

 rule large cerebella, as compared with the more inactive birds. 

 Such measurements, however, must be used with some caution, 

 as a highly developed flocculus, for example, may greatly exag- 

 gerate the apparent volume of the cerebellum. Yet it would 

 seem that the size of the cerebellum is to a large extent regu- 

 lated by the habits ot flight of the bird independently of tax- 

 onomic relations, though much more extensive observations 

 would be necessary to establish the generalization for the Aves 

 as a whole. 



Hydrochelidon nigra, the black tern, is remarkable for the 

 large dimensions of the brain. As above noted, the cerebellum 

 is relatively larger in this bird than in any other whose measure- 

 ments are recorded. The cerebrum, too, is larger than that of 

 many birds which are placed far above it in the taxonomic 



series. The 1 l b. d. is 77.9, which is not equaled by any cere- 

 brum below the 7?^//i?;r.y in Professor Turner's tables. It will, how- 

 ever, be noticed that the large cerebellum is crowded forward so 

 as to divaricate the cerebral lobes behind and thus to increase 

 the apparent width of the cerebrum. This introduces a source 

 of error which must be taken into account in making compari- 

 sons with other birds. The low rank of this bird is clearly indi- 



