Lect. IV.] DYING OUT OP THE TEETH. 101 



The youngest embryo of an Edentate worked out by 

 me was that of a Pangolin (Manis), and the likeness 

 of the skull in this stage (the embryo being only the 

 size of the little finger) to the skull of a bird is very 

 great. 



In the Crocodile's embryo, when the teeth are just 

 appearing, but have influenced the form of the jaws 

 very little, and in the embryo of the bird, at about the 

 middle of incubation, we have excellent subjects for 

 comparison with the early stage of the Pangolin. 



The Pangolin, albeit one of the Eutheria, is in 

 reality but little advanced above the Marsiipial platform. 

 The simple form of its facial bones, not hypertrophied, 

 to make room for the teeth, is excellently fitted for 

 special morphological observation ; we have the essential, 

 without the non-essential, in these parts. On the whole, 

 this skull is very much like that of an Insectivore at the 

 same stage, but the interpretation is made easier in this 

 case by the more primitive form and condition of the 

 investing or superficial bones. 



If the skull had been arrested at the stage I refer to, 

 the difiiculty would have been to separate it, as a tjrpe, 

 from the skulls of the Sauropsida (Birds and Reptiles) 

 generally. But, gradually, after the middle of the 

 intra-uterine period, changes take place in the structure 

 of the various parts, that ultimately amount to what is, 

 practically, a thorough metamorphosis. 



The changes I am now about to discuss are so great 



