RESULTS OF PALJEONTOLOGICAL RESEARCH 45 



to-day there is still discoverable traces of tooth-bearing 

 jaws. 1 Furthermore the so-called medial eye on the 

 head, which was well developed in many palseonto- 

 logical reptiles, has retrograded and been lost. In 

 Hatteria this relic of a long-vanished world the 

 medial eye is still existent but is hidden under an 

 opaque skin. 2 



These evidences of retrogression, which appear in 

 the forms of the present day as so-called ( rudimentary 

 organs/ have, in the opinion of palaeontologists, con- 

 tributed much to the transformation of the animal 

 world. The alteration frequently extends only to 

 a system of organs which, by reason of a transfer to 

 a new mode of life, have become superfluous, and 

 frequently only to a part of same ; hence in the opinion 

 of many investigators the so-called fins of the whale are 

 a positive adaptation of the front limbs to swimming, 

 and thereby no retrogression but a ( specialization/ 

 while the hinder parts (legs and pelvis) have dwindled 

 and now only remain as an insignificant bony rudiment 

 buried within the fat of the whale. 



This, however, brings us already to the so-called 

 convergence evidence. 



(6) Evidence of Convergence. It is frequently 

 observed that animals which, systematically, stand 

 far apart, exhibit changes in the same direction and 

 develop these further, so that by their further evolu- 

 tion they approach each other nearer than they were 



1 Deperet-Wegner : Die Umbildung der Tierwelt, p. 202. 



2 Ibid. 



