484 



Prof. T. J. Parker. 



[Mar. 22, 



tracts ; the ventral tract appears in Stage G. In the ripe embryo 

 and even in the adult, besides the narrow ventral space recognised by 

 Nitzsch, there are well-marked lateral spaces separating the dorsal and 

 ventral, and the dorsal and femoro-crural tracts from one another. 



In the full paper a table and diagrams will be given showing the 

 length of important parts of the body (head, beak, limbs, &c), in the 

 various stages, expressed as percentages of length of vertebral column. 

 The table shows that while the wings attain their maximum relative 

 size in Stage F, the legs continue to increase in proportional length 

 some time after hatching. The brain-case, also, undergoes from 

 Stage Gr onwards a proportional diminution in size, while the beak 

 increases steadily up to adult life. 



The greater part of the full paper will deal with the skeleton : a 

 detailed description will be given of the entire skeleton at about the 

 time of hatching, when all the more important ossifications have 

 appeared and but little ankylosis has taken place. 



The vertebral formula is — 



t K \ 



Cv. 16. Th. 5 + 3 : L. 8 : S. 3 : Cd. 3 + 6-8. 



The bracket indicates that the last three thoracic, all the lumbar 

 and sacral, and the first three caudal vertebras are united to form the 

 compound sacrum of the adult. 



The axis vertebra is ossified by five centres, the additional one 

 occurring in the antero-ventral region of the body, below the 

 odontoid ; this evidently represents an inter-centrum or inter- vertebral 

 wedge-bone. 



The cervical ribs appear to chondrify separately from the rest of 

 the vertebrae ; but further observations are needed on this point, as 

 well as on the autogenously ossified transverse processes of the sacral 

 vertebrae which in the youngest specimen hitherto examined are 

 continuous with the vertebras. 



The skull differs so little except in details from that of other birds, 

 that there is little to be said about it in an abstract. The chondro- 

 cranium of the ripe embryo and the separate membrane bones will be 

 fully described and figured. As in other birds, I find no trace of 

 Jacobson's organ ; the capsule of the organ is, however, represented 

 by a distinct (paired) rod of cartilage in the vomerine region, as in 

 Rhea. 



In Stages D — Gr the shoulder-girdle consists of a solid piece of 

 cartilage having much the same shape as the adult bone. In Stage H 

 an ossification appears in the scapular region, and another in the post- 

 axial moiety of the coracoid region. In Stage I a fenestra appears, 

 immediately pre-axiad of the coracoid ossification, dividing the 

 ventral portion of the shoulder-girdle into procoracoid and coracoid 



