ONTOGENY AND PHYLOGENY OF THE STERNUM 71 



When we come to consider the living reptiles the material and 

 evidence is abundant and of the greatest significance. 



Among the recent forms, Goette (77) has studied Cnemido- 

 phorus. While he does not show conclusively that the two an- 

 terior triangular rudiments are products of the nearby coracoids, 

 he demonstrates that only the first ribs have reached and attached 

 themselVes to the sternum, while that part of it opposite the 

 second and third ribs is formed independently of them, as a 

 backward prolongation of the anterior paired rudiments. 



These results of Goette showing that the sternum is the result 

 of a backward growth of tissue from an anterior portion are in 

 striking anticipation of what Paterson claimed to see in the rat, 

 where it is stated that the anterior median portion of the sternum 

 is derived from the same element as is the shoulder-girdle, and 

 this in turn yields the sternal bands as posterior prolongations. 



Anguis fragilis (fig. 25) has a sternum that in many respects is 

 typically amphibian in character, as may be seen at once by a 

 comparison of this form with that of Pipa. As in Pipa, there is 

 only present an anterior or presternum, separated by sutures only 

 from the epicoracoids, and as in Pipa, ossification and the amount 

 of soft cartilage around the borders are the same for sternum and 

 coracoids. Of this form Parker ('68) says, "there is a well devel- 

 oped sternum, not continuous with the ribs; " and Rathke, describ- 

 ing two embryos of Anguis, says, "with the coracoids the sternum 

 was intimately united, but it was not very closely connected with 

 the neighboring ribs, lying at a much greater distance from them 

 than in adult Blindworms. There cannot be any doubt that in the 

 Blindworms the two latter halves of the sternum do not .... 

 originate under the ribs, and unite with them, but develop at a 

 distance from the ribs. " Barring the presence of the interclavicle 

 in Anguis, it would be difficult to recognize this shoulder-girdle 

 as being that of a reptile, for in the relations of its girdle and pre- 

 sternum and in the absence of ribs it is characteristically 

 amphibian. 



Stellio cordylinus (fig. 26) has a sternum in which the anterior 

 part is enormously enlarged; is in intimate relation to the epi- 

 coracoids, and in addition has two greatly extended xiphisternal 



