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ON THE EAELY DEVELOPMENT OF THE APPEN- 

 DICULAE SKELETON OF THE OSTEICH, WITH 

 EEMAEKS ON THE OEIGIN OF BIEDS. 



By E. Broom, M.D., D.Sc., Victoria College, Stellenbosch. 



(Eead June 27, 1906.) 



(Plate IX.) 



Though the structure of the skeleton of the adult ostrich has been 

 fully known for many years, almost nothing has been done, so far as 

 I am aware, in the study of the early development. As the ostrich is 

 one of the most primitive birds at present alive, it seemed to me 

 advisable that the early condition of the skeleton should be examined, 

 as it might possibly throw some light on the ancestry of the birds. 

 Jeffery Parker has carefully studied the development of the skeleton 

 of the Apteryx, and Kitchen Parker, besides his work on the develop- 

 ment of the skull of the ostrich, domestic fowl, and other birds, has 

 done much to elucidate the development of the avian appendicular 

 skeleton. The early development of the bird's pelvis has been 

 studied by Johnson and Mehnart, the early stages of the wing 

 by Leighton in Sterna, and the early stages of the shoulder girdle 

 and sternum of various birds by Miss Lindsay. 



The study of the early condition of the ostrich skeleton confirms 

 many of the facts discovered in other birds, and also enables us to 

 add one or two points of interest. 



I have examined two stages of the ostrich embryo, the one of 

 10 days' incubation and the other of 11 days. These are approxi- 

 mately equal to the 7- and 8-day embryos of the domestic fowl. The 

 shoulder girdle and pelvis have been studied by tangential and 

 transverse sections and the limbs by series of sections in the planes 

 of the manus and pes. 



Shoulder Girdle and Sternum. 



The shoulder of the adult ostrich differs from that of all other 

 birds in having a large cartilage bone lying iu front of the 



