214 RE GENERA TION 



a maxilliped is cut off a structure different in kind often regenerates, 

 but that after several months the typical structure returns. Do we find 

 here an ancestral organ that first appears, and then gives way to its 

 more modern representative ? If it resembled the maxilliped of any 

 other crustacean, the evidence would, no doubt, be accepted by those 

 who accept the evidence furnished by Miiller. What then shall we 

 say to the case, first discovered by Herbst, in which the eye of cer- 

 tain prawns being cut off, an antenna-like organ regenerates? Since 

 these antennae are similar to those possessed by the same animal, 

 shall we assume that it once had antennae in place of eyes ? 



Another comparison, that Fraisse has made, is worth quoting as 

 showing how far credulity may be carried. In the regeneration of the 

 tail of certain lizards pigment first appears in the ectoderm of the new 

 part and then sinks deeper into the layers. Fraisse found a lizard on 

 Capri in which the tail is pigmented throughout life, and although he 

 did not know whether or not the pigment is in the skin he suggests 

 that this lizard represents an ancestral condition, that is repeated by 

 the regenerating tails of other forms. 



Boulenger ('88) pointed out that the scales over the regenerated 

 tail of several lizards have a different arrangement from that of the 

 normal tail, and furthermore, the new arrangement is sometimes like 

 that found in other species. He claims that this shows that such forms 

 are related, even where no evidence of their relation is forthcoming. 

 That the conditions in the new tail may be different from those in 

 the normal tail is shown by the absence of a vertebral column, etc. ; 

 therefore that the scales also should have a new arrangement is not 

 surprising, but the facts fail, I think, to show that there need be any 

 genetic relation between the forms in question. That the conditions 

 in the new tail might be like those in an ancestral form may be 

 admitted, but this is very different from assuming that the results 

 show a genetic relation actually to exist. The main point is that, 

 even if the results should be nearly identical, it may be entirely mis- 

 leading to infer that ancestral characters have reappeared. 



In some cases an extra digit or toe may regenerate on the leg of 

 a salamander, and this too has been interpreted as a return to an 

 ancestral condition. But Tornier has shown, as has been stated, 

 that several additional digits, or even a whole extra hand, may 

 be produced by wounding the leg in certain ways, and these too 

 would have to be interpreted as ancestral, if the hypothesis is carried 

 out logically. It has been shown by King that one or more additional 

 arms may be produced in a starfish by splitting between the arms 

 already present, and if we accepted evidence of this sort as having 

 any value in interpreting lines of descent we should conclude * that 



1 King pointed out the fallacy of this argument. 



