504 BIRDS. 



DIAGRAM XXX. 



Birds. 



The figure named Brain shows the cerebral hemispheres {cer. h.) 

 with small olfactory lobes (plf.), the cerebellum (cerebell.), the pineal 

 body (p. b.), the optic lobes {opt.), the medulla oblongata (m. o.). 



Skull (after W. K. Parker) shows the position of the following bones : — 

 parietal (p.), frontal (/), post-frontal process (p.f-), mesethmoid (me.), 

 lachrymal (/.), premaxilla (px.), maxilla (mx.), vomer (v.), pterygoid 

 (pt.), quadrate (g.), squamosal (sq.), jugal (/.) quadrato-jugal {q. j.), 

 dentary {d.), angular (a), articular (ar.). 



Arm (after W. K. Parker) shows humerus {h.), ulna (a), radius (r.), 

 the ulnar carpal («'), the radial carpal (Z), the three united metacarpal 

 (marked //. and ///.), the phalanx of the thumb (marked /.), the 

 phalanges of the other two digits. 



The Feather-germ (from Wiedersheim) shows the dermis {Derm.), 

 the feather-follicle {F.), the stratum Malpighii {s. m. ) and the stratum 

 corneum {s. c, ) of the epidermis. 



Blast I. (after Balfour) shows in section the segmented area or blasto- 

 derm {bl. ) on the top of the yolk {y. ), with the segmentation cavity (j. c. ) 

 between them. 



Blast II. (atter Balfour) is a surface view of the blastoderm, /. j. the 

 primitive streak, m. g. the medullary groove, h. f. the incipient head- 

 fold, am. f. the incipient amnion-fold. 



Egg (after Allen Thomson) shows a diagrammatic section of the egg, 

 the shell (j. ), the outer shell-membrane {s. m.), the inner shell-mem- 

 brane {i. s. VI.), the air-chamber {a. ch.), the white of egg {^h.), the 

 chalazas {ch.), the vitelline membrane {v. m.), the yolk {y.) with white 

 yolk in layers among the (dark) yellow yolk, and forming also a central 

 mass, the position of the incipient blastoderm {bl.). 



