REGENERATION I 1 5 



sally true, it would nevertheless not be a convincing argument 

 for tlie above view, although it would certainly support it. But 

 a closer examination into the facts shows that this statement is 

 not absolutely correct. Although the capacity for regeneration 

 is never so far-reaching in the highest animals as it is in the 

 case of the lower ones, — and this must be due to some cause. 

 — the regenerative power may nevertheless even vary widely in 

 animals of the same degree of organisation, and may in fact 

 be far greater in one of the higher than in one of the lower 

 torms. Thus fishes are unable to regenerate a lost pectoral or 

 pelvic fin. while the much more highly organised salamander 

 has been known to regenerate a limb six times in succession 

 (Spallanzani). 



The regenerative power often varies in degree even within 

 the same group of animals. In Triton and SahDnandra the 

 entire limb grows again after amputation, but apparently, so far 

 as I Iia\e been able to obser\e, this does not occur in Proteus. 

 The tail. too. is only replaced slowly and imperfectly in the latter 

 animal, whereas it easily becomes restored in the salamander. 

 In the year 1878 I received a Wxing Siren lacertiiuu the fore-limb 

 of which had Ijeen torn oiT, so that onl\- the stump of the upper 

 arm remained, and the entire limb did not ijrow again in the 

 course of the ten years during which I kept the voracious animal, 

 and gave it abundant food. In this case again the power of 

 regenerating the extremities seems to be less than in that of 

 salamanders, which are mucli younger phyletically, and much 

 more highly organised. 



It is well known also that the limbs of a frog do not grow- 

 again when they have been cut off, even when the animal is in 

 the larval condition. The fact that the regenerative power can 

 vary so considerably within the same genus is still more re- 

 markable. Schreiber observed that the power of regeneration 

 in Triton inarnioratus is relatively very slight as compared with 

 that which is possessed by all other species of Triton which 

 have been examined for this purpose. 'In captivity, at any 

 rate, even slight injuries in sucli parts as the crest are never re- 



that the power of reproducing lost parts is greatest where the organisa- 

 tion is lowest, and almost disappears where the organisation is highest. 

 And though we cannot say that between these extremes there is a constant 

 inverse relation between reparative power and degree of organisation, yet 

 we may say that there is some approach to such a relation.' 



