260 THE EVOLUTION OF THE METAZOA 



influence of the Theory of Evolution when everyone was 

 eager to find further proofs of the descendence theory, scholars 

 became convinced that these larvae must represent something 

 more than a transitional stage only in the individual ontogenies. 

 Following the example of Darwin, Miiller, and Haeckel, schol- 

 ars became used to the concept of recapitulations. Yet here 

 they have made a mistake which appears rather insignificant 

 at first sight and which has been afterwards pointed out by 

 several critics, above all by Garstang. On one hand they have 

 confounded the repeated (yet changeable) ontogenetic stages 

 with the adult forms of ancestors, and on the other hand they 

 believed in a recapitulation not only of individual charac- 

 teristic properties of the ancestral embryos and of larvae but 

 also of whole ontogenies or at least of whole stages as such. 

 These methodological blunders have proved fatal. A large 

 amount of honest and intensive work was made completely 

 useless. Numerous theories and hypotheses were proposed 

 and courageously defended which were built on the basis of 

 the so-called "fundamental biogenetic law." As an example, 

 I wish to mention here the famous trochophore theory as it 

 was formulated by Berthold Hatschek, an ingenious zoologist 

 and my greatly admired teacher. Yet in spite of all this, these 

 theories can still contain some useful elements, they still have 

 some element of truth in them. There can be no doubt that 

 recapitulations take place and that the comparative morpho- 

 logy of larvae can prove as useful and informative for our 

 phylogenetic speculations as is the comparative morphology of 

 embryos; provided that it is taken from the right angle and 

 that the probability of true recapitulations is kept within 

 limits. Mistakes of the old type continue to be made down 

 to the present day as can be seen in the case of Endoprocta 

 (Kamptozoa) that have been united with Ectoprocta into a 

 new group Bryozoa because of certain similarities that can 

 be observed in their larvae. 



There have been three main reasons which induced 

 scholars to see in larvae a recapitulation of an ancestral form. 



