98 



INTRODUCTION. 



whereas the transformed tailless Batrachians, unlike 

 their tailed precursors, occupy too high a position in 

 the zoological scale to be able to regenerate ampu- 

 tated extremities, the hind limbs reproduce without 

 difficulty during the larval existence, a fact first 

 observed by Spallanzani in the last century, and 

 since verified by Giinther and Barfurth. In order 

 to be regenerated it is, however, necessary that the 

 limb be not completely removed. A basal fragment 

 of the femur must remain to give off the cartilage- 

 cells which, most curiously, will become differentiated 

 into the various segments, proceeding from the distal 

 to the proximal ; and the mutilation must have taken 

 place some time before the close of the third larval 

 period or true tadpole stage. It has been stated that 

 reproduction of the limbs can only be obtained in 

 young larv£e, long before they have reached their full 

 size. This is, however, contrary to my own experience 

 on large, full-grown tadpoles of Alytes ohstetricam, in 

 which the well-developed hind limb, after having been 

 amputated below the knee-joint, was regenerated with 

 the greatest facihty. 



Fig. 41. 



Series of embryos of Bomhinator pachypus. (Alter Goette.) 

 Showing tiie formation of the larval mouth, together with the 

 atrophy of the adhesive disks; the gradual disappearance of 

 the external gills, and the formation of the median spiraculum 

 hy approximation of the two opercular slits ; and the develop- 

 ment of the gut (the abdominal membranes being removed). 



