512 



way. These sporadic appearances of cartilage in typical membrane 

 bones seem to be of no morphological importance. 



The malleus of the foetus is entirely cartilaginous. It articulates 

 with the incus by a twisted concave face. From below, the manu- 

 brium runs horizontally forwards parallel to Meckel. There in no 

 evidence of its having a separate origin from the body of the malleus, 

 as KiNGSLBY found in the Pig, but in agreement with Fraser's work 

 on some of the higher mammals, and Broom's on Dasyurus, it is 

 found to develop later than the body. In fact, it chondrifies very 

 considerably later. Long after the body has acquired the structure 



Fig. 2. Internal view of same. Lettering as above. 



of hyaline cartilage, the manubrium remains in a procartilaginous 

 condition. The evidence seems to show that the manubrium is a 

 secondary and later developed process of the malleus. 



The membrane ossification below the malleo-meckelian bar has 

 been noticed by most authors. It is a shallow through fitting below 

 on to Meckel's cartilage and is quite free from any other jaw element. 

 In previous work it has been- interpreted as the angular, but the evi- 

 dence given below does not favour this suggestion. 



The incus, like the malleus, shows as yet no ossification, but in 

 general form, with its thick body and two crura, it closely resembles 



