Karl Pearson and Adelaide G. Davin 
38.5 
again ;iiid in a different direction as we reach the shaft. Their arrangement seems 
to us not inconsistent with a separate centi'e of ossification for the fibuhir crest. 
Our view differs fron) that of Dr Mackenzie and Mr W. Owen, histologist to the 
Australian Institute. They speak of section A of the embryo as if it were wholly 
cartilaginous. It seems to us as if a portion of this superstructure of the fibula does 
show ossification starting (Plate XXXVII, Fig. i)G). The articular process of fibula, 
section B of Fig. B below, has a distinct centre of ossification in the embryo. 
Further the section at C also shows ossification and Dr Mackenzie tells us that 
FiR. A. 
Fig. B. 
there is (>ne at the distal end (section not forwarded). There would thus appear t(,> 
be four centres of ossification, of which only three are to be found in the higher 
Mammals. The suggestion is that the fourth centre of ossification is at the basis of 
the parafibular sesamoid of the Marsupials, oi' the later cywinellu and lateral fabellu. 
If the above view be correct that the Mammals with lateral sesamoids of the 
knee-joint ai-e descended from a primitive mammalian foi'm with a crested fibula, we 
should anticipate that still lower in the evolationary scale, e.g. in the Aves or 
Reptilia, no lateral fahella or cyamella will be discoverable. It may be objected 
