1898.] 



SKELETON OP ALYTES OBSTETEICANS. 



103 



as Grotte (10) and Strasser (13) bave shown, the first digit to 

 develop is the second ; the inner digit follows and then the 

 remaining digits in succession, the third, the fourth, and, in the 

 hind limb, the fifth. The digits of the normal Anuran limb, 

 however, develop simultaneously, as Grotte (9) has remarked in 

 the case of Rana and Hyla, and as Duges has figured in the case 

 of Pelohates (5. pi. additionnelle, figs. 11-13). Tour figures of the 



Eigs, 1-5. 



Skeleton of regenerated left hind limbs of Ali/tes obstetrkans ( x 5). 



budding normal hmb of Alytes are here given (figs. 6-9, p. 104) to 

 illustrate this point farther, and it will be noticed that, so soon as 

 any digitation at all can be made out in the differentiating bud, 

 all five digits can be counted. The explanation usually given for 

 the exceptionally rapid development and the great length of the 

 first-formed digits in the newts is that these are larval digits, of 

 special functional importance to the larva. But in the Anuran 

 tadpole the paired limbs are not used as a means of progression ; 

 they simply develop passively and slowly in anticipation of the 

 approaching metamorphosis. It is curious, therefore, to find that 

 in the regenerated limb of Anuran tadpoles the TJrodele mode 

 of digit-development should he adopted. 



