140 Facts Compelling Us to Reject Pre formation 



processes which are essentially identical with each other, 

 but has been thereby driven to an attempt at explanation, 

 which is wholly artificial and indefensible. 



In order to make the artificiality of his interpretation 

 of the most difficult cases clearer, let us consider further 

 the following examples. 



It is known that regeneration is not usually an exact 

 repetition of the ontogenetic process. 



"Until the last few years," writes Delage, "it has been 

 regarded as a dogma that regeneration is a repetition of 

 ontogeny. That is that the regenerating organ or limb 

 goes through the successive stages of development 

 through which it went in its first formation. Yet the 

 question has not been thoroughly enough investigated to 

 permit the statement that it always does this, and in many 

 cases it is certain that it does not proceed in this way. 

 Thus a round tailed salamander regenerated a round tail 

 from the first and not the flattened finlike tail of the larva, 

 the crab regenerates an adult foot and not a foot like that 

 of its larva, Zoaea. The limb or organ regenerated after 

 a wound arrives at once at the stage which corresponds to 

 the age at which regeneration takes place." m 



Further, regenerations of ectodermic tissues at the 

 expense of entodermal or mesodermal tissues are not 

 rare. We have already seen how the crystalline lens, 

 embryologically of ectodermic origin, regenerates in the 

 triton from the mesodermic iris. The anterior intestine 

 of Tubifex rivulorum, whose ontogenetic origin is 

 ectodermal, regenerates, with the exception of a small 

 portion at the end, from entodermal tissues. 115 



114] 

 1161 



'Delage : L'heredite etc. P. 104 105. 



'H. Haase : t)ber Regenerationsvorgange bei Tubifex rivulorum 

 Lam. mit besonderer Berucksichtigung des Darmkanals und Ner- 



