360 Transactions of the South African Philosophical Society. 



Parker in Apteryx. At first sight it might well seem superfluous to 

 repeat such work even with a new type, but every one who has 

 worked much at skeletogenesis will admit the very great difficulties 

 of the subject — difficulties which lie not in the appearances so much 

 as in the interpretations of the appearances. When cartilage is 

 developed there is no difficulty in reconstructing and drawing the 

 chondrified elements ; the difficulty is with the procartilage — 

 elements or parts of elements which are going to become cartilages 

 or which ought to become cartilages but never succeed. In a good 

 deal of the work which has been done in early embryos the difficulty 

 is got over by ignoring the procartilage and only figuring the carti- 

 lage. But this method is comparatively useless. The procartilage 

 is much more important to the morphologist than the cartilage, as it 

 is the procartilage more than the cartilage that recapitulates the 

 .ancestral characters and throws light on the phylogeny. And in 

 dealing with early embryos it is frequently well-nigh impossible to 

 differentiate procartilage from other condensations of cells. 



In the 10-day ostrich embryo the pelvis is well developed and 

 much of it is chondrified. The ilium is of large size and is developed 

 both much in front of the acetabulum and far behind it. The pre- 

 acetabular portion is a deep, flat plate, which extends forwards in the 

 direction of the lumbar vertebrae. Posteriorly the ilium narrows 

 very considerably and curves downwards and backwards along 

 the curved caudal vertebrae. The acetabulum is relatively of 

 large size and is imperforate, being completely closed by the ilium, 

 pubis, and ischium. The pectineal process is of large size, but it 

 appears to be formed by the pubis rather than the ilium. If this be 

 so, then the head of the pubis is unusually broad. The lower part 

 passes downwards and curves slightly backwards, and is a slender, 

 cartilaginous rod. At its lower end it passes into a broad sheet of 

 procartilage which connects it with the ischium. Near the lower 

 end of the cartilaginous portion a slight condensation of connective 

 tissue or procartilage cells probably represents the early stage of the 

 prepubis. The ischium has a very broad head which joins with the 

 ilium and the pubis, and forms much of the acetabulum. From this 

 it passes downwards as a broad bar of cartilage, then curves forwards 

 as it passes into the sheet of procartilage, which unites it with the 

 lower end of the pubis. There is no symphysis of the pubes or ischia, 

 ■each being a considerable distance away from its neighbour of the 

 opposite side. 



In the 11-day embryo the condition of parts is much more like 

 that of the adult. The pectineal process, though still large, is rela- 

 tively much smaller. The pubis and ischium are longer and relatively 



