310 



REGENERATION 



The tadpole tail regenerates rapidly. This may be due in part to the embryonic nature 

 of the cells contiguous to the cut surface. The initial axis of regeneration is generally 

 at right angles to the cut surface but this is rectified subsequently. Twitty and Delanney 

 (1939) found that the tail of Amblystoma is capable of repeated regenerations after suc- 

 cessive amputations even during long periods of continuous starvation. There is a grad- 

 ual decrease in the rate (and degree) of regeneration as amputations are performed later 

 in larval life {Goodwin, 1946); and newly hatched larvae respond the better possibly be- 

 cause they have incompletely differentiated tissue which can be more simply de -differ- 

 entiated to form a blastema, and then re-differentiate as required. 



Most Urodeles retain their powers of regeneration throughout life, but to a lesser degree 

 after metamorphosis. The Anura, on the other hand, lose most of their regenerative 

 powers after metamorphosis. However, there is recent evidence (Butler, Rose, Schotte, 

 and Singer) that even the Anuran appendage will exhibit some powers of regeneration pro- 

 viding (Rose) the cut surface is continually irritated by hypertonicity with NaCl, or 

 (Butler, Schotte, Harland and Singer) the connection of the appendage with the central 

 nervous system is not interrupted. Schotte and Butler (1941) have demonstrated the re- 

 gression of the humerus in a denervated limb of Amblystoma. In fact, these investiga- 

 tors make the statement that: "No blastema is ever established on a completely nerve- 

 less amputated limb. " 



%3 



Regression of skeleton of forelimb 

 (Amblystoma) following denervation. 

 (Total time 52 days) 



(From Schotte G Butler 1941: 

 Jour. Exp. Zool. 87:279) 



*— ^^^ C^^ ^"^=1:^* 



Sept. 17 



Oct. 7 



Regeneration of foot and digits of Rana 

 pipiens pre-metamorphic tadpole hind- 

 limb. Photo taken 24 doys after trans- 

 verse cut made at shank level. 

 (P. Bernstein) 



