564 THE WONDER OF LIFE 



followed by re-growth. The new wing is at first homogene- 

 ous and transparent, it subsequently gets veins which 

 seem to be after the normal pattern. The regeneration of 

 a wing has also been observed in the meal-beetle (Tenebrio). 

 In Nature an insect bereft of wing would be likely to die, 

 nor is the accident very likely to happen often unless in 

 Lepidoptera, where the removal of a wing is followed by no 

 result. It seems difficult therefore to suppose that the 

 regenerative capacity is always adaptive. 



An interesting peculiarity in connection with regenera- 

 tion in the starfish may also be used as a test case. Miss 

 Helen D. King points out that in Aster ias vulgaris it is 

 quite usual for an isolated arm to regenerate the whole if 

 it has a fraction of the central disc left. ' Comet-forms ' 

 are not infrequent, which consist of a fully- developed arm, 

 a partially formed disc, and four beginnings of the arms 

 which are missing. One of these forms is figured (Fig. 91), 

 and every shore-naturalist is familiar with every possible 

 transition between the single arm and the intact starfish. 

 All this is well known, but what Miss King's experiments 

 brought out was the fact that while the ventral part of 

 an arm may regenerate the dorsal surface, the converse 

 does not occur. It may be said, of course, that this is 

 simply because of the complexity of the ventral surface, 

 with its tube-feet, water-vessel, nerve-strand, and so on. 

 But it is just possible that the reason may be different, and 

 connected with the obvious fact that the dorsal surface is, 

 in natural conditions, much more open to attack and injury 

 than the ventral surface which adheres to the rock. Again, 

 perhaps, the exception proves the rule. 



Another apparent difficulty which turns out to be a 

 corroboration is expounded by Bordage. The lower or 



