THE APPENDICULAR SKELETON. 215 



the same time, now lies, as in the adult, almost parallel to the 

 backbone ; and the hip joint is shifted to the extreme hinder 

 end of the body. 



c. The limbs. The skeletal framework of each limb develops 

 from the proximal towards the distal end ; the humerus and the 

 femur being the first bones to be differentiated. The radius and 

 ulna, and the tibia and fibula, are at first independent of each 

 other, but the cartilages of each pair soon fuse. Of the digits, 

 the two preaxial, radial or tibial, of each limb are established 

 first : the others budding out in succession. There is some 

 doubt as to which of the normal five digits is absent in the 

 hand of the adult frog ; and the embryological evidence, though 

 not conclusive, is rather in favour of the view that it is the fifth, 

 and not, as is commonly held, the first digit or pollex that is 

 wanting. 



List of the more important Publications dealing with the Develojjmenl 



of Frogs. 



Alcock, T. : ' On the Development of the Common Frog.' Memoirs of the 



Manchester Literary and Philosophical Society, series iii., vol. viii. 1883. 

 Assheton, R. : ' The Development of the Optic Nerve of Vertebrates.' Quarterly 



Journal of Microscopical Science, vol. xxxiv. 1892. 

 Balfour, F. M. : 'A Treatise on Comparative Embryology,' vol. ii. 1881. 

 Bambeke, C. van: ' Recherches sur le Developpement du Pelobate brun.' 1867. 

 ' Nouvelles Recherches sur 1'Embryologie des Batraciens.' Archives 



de Biologic, i. 1880. 

 Barfurth, D. : ' Versuche fiber die Verwandlung der Froschlarven.' Archiv 



fur mikroskopische Anatomie, xxix. 1887. 



' Die Riickbildung des Froschlarvenschwanzes und die sogenannten 



Sarkoplasten.' Archiv fur mikroskopische Anatomie, xxix. 1887. 

 Bedot, M. : ' Recherches sur le D6veloppement des Nerfs Spinaux chez les 



Tritons.' Archives des Sciences Phys. et Nat., xi. 1884. 

 Boas, J. E. V. : ' Ueber den Conus arteriosus und die Arterienbogen der Amphi 



bien.' Morphologisches Jahrbuch, vii. 1881. 



' Beitrage zur Angiologie der Amphibien.' Morphologisches Jahr- 

 buch, viii. 1882. 

 Bourne, A. G. : On Certain Abnormalities in the Common Frog.' Quarterly 



Journal of Microscopical Science, xxiv. 1884. 

 Cope, E. D. : ' On the Relations of the Ilyoid and Otic Elements of the Skeleton 



in the Batrachia.' Journal of Morphology, ii. 1888. 

 Duges, A. : ' Recherches sur 1'Osteologie eb la Myologie des Batraciens a leurs 



differents Ages.' Memoires de 1'Academie des Sciences. Paris. 1835. 

 Duval, M. : 'Sur le Developpement del'AppareilGenito-urinairede la Grenouille. 1 



Revue des Sciences Naturelles. 1882. 



