624 R. M. STRONG 
bination is usually designated as an olfactory lobe and will be 
so termed in this paper. 
In Apteryx, the olfactory lobes are of considerable size accord- 
ing to the figures of Owen (72, pl. xlv, fig. 2). This writer says 
(p. 383), that the ‘‘Rhinencephalon is as remarkable for its large 
size as is the mesencephalon for the smallness of its principal 
elements,” in Apteryx. The optic lobes and nerves are small in 
Owen’s figures. The only other reference to very large olfactory 
lobes in a bird is that of Klinckowstrém (’90), who figured and 
described large olfactory lobes for Fulmarus glacialis. 
The olfactory lobes of a number of birds were studied by Bumm 
(83) who noted that these structures are smaller in birds than in 
mammals. He states that the olfactory lobes are well developed 
in the swimming birds, moderately large in the marsh birds 
(‘sumpf V6geln’), and much less developed in other orders. 
The ratios in weight of the olfactory lobes to the cerebrum are 
given for the ‘Gans,’ ‘Schnepfe,’ and ‘ Bussard.’ 
Some statistics are given for the olfactory lobes in forty-two 
species of American birds, the majority being Passerine forms, by 
Turner (91). Turner concluded that ‘‘there has been a gradual 
retrograde evolution of the avian rhinencephalon”’ (’91, p. 57). 
He observed that ‘‘as we ascend the scale, the olfactory lobes 
move caudad and become smaller,’ and he also noted that they 
are fused and almost completely imbedded in the ‘prosenceph- 
alon’ in the higher groups. In another article, Turner (91b), 
stated that the high development of the sense of vision in birds 
has been accomplished at the expense of the olfactory sense. 
The histological structure of the bird olfactory lobes has been 
described by Turner (91), and by Pedro Ramon y Cajal. The 
latter’s account was not accessible to the writer, and it has been 
necessary to depend upon the statement of Edinger (’03, p. 403) 
of Cajal’s conclusions. The structure is stated to be of the same 
type as in other vertebrates except for being simpler. 
References to the olfactory lobes have also been made by Carus 
(14), Elliot-Smith (95), Stieda (’69), Herrick (93) Schiipbach 
(94), and Kappers und Theunissen (’08). 
