ONTOGENY AND PHYLOGENY OF THE STERNUM 67 



This description of two cartilaginous bands appearing in the 

 inscriptiones tendineae is strikingly similar to the account of 

 the sternal bands in the pig by Whitehead and Waddell. There 

 seems to be no antagonism anywhere to the view that in the 

 Amphibia the anterior part of the sternum is the product of the 

 shoulder-girdle. 



Nor is it necessary to stretch any morphological relations 

 unduly to see this coracoidal sternum reproduced in the Dipnoi, 

 Gobius, Polypterus, and Notidanus. We must agree with 

 Parker ('91), Has well ('84), and others, that the sternum in the 

 Ichthyopsida is coracoidal in origin and homologous throughout 

 that group. 



From here on, however, we part company with all early 

 workers, and most later ones as well, for all of them accept 

 Ruge's conception of a costal sternum in the Amniotes, and 

 deny any homology between the sterna of Ichthyopsida and 

 Amniota. One of the designs of this present phylogenetic 

 sketch is to show from figures and data already in the literature 

 that the two are one and the same thing in origin and develop- 

 ment, and therefore homologous. 



As practically all are agreed that the sternum in the Amphibia 

 is coracoidal in origin, while but few are agreed that it is so in 

 the Amniotes, we are brought to the necessity of bridging in 

 some manner the alleged gulf between the amphibian and 

 reptilian sternum. 



In order later to make direct comparisons between amphibians 

 and reptiles, when treating the latter group, it is necessary to intro- 

 duce here a number of figures and remarks thereon for several 

 representative amphibians. Starting with the frog, figures 16 

 to 19, inclusive, give a very good idea of the development of the 

 coracoids and sternum in this form. It is hardly necessary to 

 point out the close relation between coracoid and sternum nor 

 to suggest that the figures can lead only to one conclusion, that 

 of a coracoidal origin for the sternum. 



Pipa (fig. 20) has a sternum which, as Parker says, chal- 

 lenges attention. A little study of this figure will convince one 

 that the sternal region must have been at one time a part of, and 



