The Recapitulation Theory in Biology 27 



A point of importance emphasized by Cumings deserves 

 notice here: 



"....the Hyatt school of paleontologists have based their 

 phylogenies on epembryonic [i. e., larval] rather than embryonic 

 stages .... since in the nature of the case the true embryonic 

 stages are scarcely ever accessible to the student of fossils . . . 

 There arises here a question of definition, does the biogenetic 

 law mean that the ontogeny is a recapitulation of the phylogeny, 

 or does it mean that the embryogeny is a recapitulation of the 

 phylogeny?" "In most of these cases [those listed in the second 

 paragraph above] it is the epembryonic and not the embryonic 

 stages that are the basis of comparison. " 41 



In concluding this report of the bearing of acceleration and 

 retardation upon recapitulation, it will be well to refer to a 

 significant caution contained in Cope's discussion of "inexact 

 parallelism." It has been noted that Cope used this expression 

 in part to refer to a lack of correspondence between any ontogeny 

 and its own restricted line of descent. But he used it also to 

 cover a lack of correspondence between an ontogeny of one 

 line of descent and forms in parallel lines of greater or less kin- 

 ship by reason of ancestors at different points of remoteness 

 in the past. Thus, 



"So soon as new subordinate characters are assumed.... 

 the parallelism becomes "inexact," and such is the kind of 

 parallelism usually observed. And it is the more inexact the 

 more widely removed in relationship are the forms compared. 

 Thus the parallelism between the embryo man with five branchial 

 slits, and the adult shark, it is very inexact ; but that between a 

 true fish and a shark is much less inexact. That between a 

 higher and a lower shark is still more exact, and so on." "As 

 we compare species which are more and more different the more 

 necessarily must we confine the assertion of parallelism to single 

 parts of the animals and less to the whole animal." 42 



It appears, therefore, that in the cases of perfect acceleration 

 we have just those conditions required by the logic of the theory 

 of recapitulation in its extreme form. They illustrate nicely 

 the modifications "at a not early age" that Darwin saw were 

 needed for a genetic explanation of von Baer's law, and they 

 fall into Fritz Muller's second class of cases. The evidence 



"Loc. cit.. pp. 306, 337. 



"Primary Factors in Evolution, 1896, pp. 200, 207. 



