34 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 



of his theory, but Beddard (ibid.) showed that it loses weight 

 when it is remembered that the marsupial genus Omjchognle, 

 or nail-tailed wallaby, j)ossesses a nail-like appendage on the 

 extremity of its tail ; the lion is also similarly provided. 



As mentioned above, Palaeontology does not support the 

 theory of Polydactyly, as the Stegocephali hitherto discovered 

 are never provided with more than five digits to the pes or 

 manus, and furthermore some of them may even be apodous. 

 In this connection Wood-Jones (1920, p. 16) states : " It is 

 true that Palaeontology has proved that the digitate limb may 

 possess more than five digits, but that is a very different thing 

 from demonstrating that any number greater than five repre- 

 sents a basal or primitive condition, for it is possible that the 

 increased number might be due to a secondary specialisation." 



Embryology is equally silent. In the development of the 

 Amniote limb, never more than five digits have been observed 

 in normal cases, and all the digits appear simultaneously. 

 Frequently more digits are present in the embryo than in the 

 adult, as, for example, in the Aves a rudiment of the fifth toe 

 may arise in the embryo, but it degenerates later and is absent 

 in the adult ; this, of course, being in accordance with the 

 Law of Recapitulation. In the tailed Amphibia the develop- 

 ment of the digits proceeds in a different manner, the process 

 being one of budding. The first to appear are the first and 

 second digits, then the third, fourth, and fifth in order ; and 

 according to Baur there are never more digits in the embryo 

 than in the adult. Graham Kerr also states that there is a 

 tendency for the digits of Amphibia to develop in regular 

 sequence according to the number of digits in the adult. On 

 the other hand, it must be mentioned that Bardeleben (ibid., 

 p. 256), stated that Kehrer maintains there is evidence for 

 believing heptadactyly occurs in the Urodela. 



In the Reptilia the prepollex and prehallux do not appear 

 to be well represented, but in the Amphibia Anura the pre- 

 hallux is quite a conspicuous structure. 



The Prepollex and Prehallux as the Missing Component 

 in the pollex and hallux respectively. 



Baur has suggested (1896, p. 669) that the prepollex and pre- 

 hallux are of secondary origin, but, as Comparative Anatomy, 

 Palaeontology, and Embryology do not support theories of 



