774 DESCRIPTION OF APHANTOPHRYVE 



racoid appears to strengthen, being, no doubt, influenced by the 

 tendency to counterbalance, Hable to occur in any evolutionary 

 process. 



ii. A further reduction of the clavicle marks the cessation oi 

 the increase in the procoracoid. 



iii. As the clavicle becomes almost totally reduced (as ex- 

 hibited by the genus Sphenophri/ne), and the bone can no longer 

 be said adecjuately to perform its original function in the girdle, 

 the procoracoid, which cannot replace it in supplying the neces- 

 sary support and muscle-attachment, also weakens. At this 

 stage we can notice — (a) a, reduction in the size and arrangement 

 of the pectoral muscles; (b) a correlated reduction in the size and 

 strength of the arms; (c) a marked strengthening and expansion 

 of the coracoids at the symphysis; and sometimes (d) an increase 

 in the size and strength of the sternal plate. 



(iv.) A further stage is shown by the genus Jlicrobatrachun 

 Roux, in which the clavicles appear to be quite absent, and the 

 procoracoid a weak, tape-like cartilage extending from the 

 scapula to the symphysis. 



V. Finally, we have the complete reduction of the clavicular 

 and procoracoidal elements shown in Ka/ou/a, Ilylophorbus, etc. 



It will be seen, then, that the ligament of Aphavfuphr-i/ue 

 occupies an analogous position to the procoracoid uf Micro- 

 batrachu><, but, for the following reasons, we cannot regard them 

 as homologous. There is no reason to doubt that the tape-like 

 band of the latter is a true cartilaginous procoracoid of a degen- 

 erate nature, but, in Aphaufophi-yue, it is a tough, translucent, 

 fascia-like band, which, from a macroscopical examination, I 

 have no hesitation in pronouncing a true ligament. Then, too, 

 in some species of Sphfuophrytw, the reduced procoracoid has 

 lost its connection with the scapula, but its free distal end is 

 joined to the shoulder by a true, ligamentous band. This would 

 appear to be the homologue of the ligament in question. In 

 fact, if we imagine the final reduction of the procoracoid to take 

 place along this line, we should then have a decreasing cartilage, 

 with an increasing band of ligament, which, in the end, would 



