iS93. THE RECAPITULATION THEORY. 27.7 



events not in the position that it first occupies in Antedon. It appears 

 from palasontological evidence that this plate first appeared above the 

 level of the radials, that it gradually sank down between the two 

 posterior radials, and that at a far later period, towards the close of 

 the Palaeozoic, it gradually passed upwards again, precisely as it does 

 in the young .-:!;/^£'^tf;/, and eventually disappeared. The ontogenetic 

 stages of the anal plate in Antfdoii are represented in the phylogenetic 

 series by Ceviocyinus, Erisocrinus and Stemmatocrinus. Mr. Hurst is 

 bound to suppose that such forms as Mevocrinus and Dejidyocyimis started 

 with an anal plate in a line with the radials, a supposition contrary to 

 all available evidence, or that the anal plate in Antedon, together with 

 the remarkable changes that it passes through, is a special larval 

 development. " Mystical " it may be, to suppose that we have here 

 an epitome of the ancestral history, but Mr. Hurst can hardly say 

 that it is not justified by evidence. 



There are many other curious parallelisms between the growth of 

 Antedon and the history of the earlier crinoids. It is, however, 

 possible to explain them on Mr. Hurst's plan, so I merely allude to 

 them here to show that they do not in any way run counter to the 

 Recapitulation Theory. They are the large size of the basals, the 

 peculiar shape of the radials, the well-developed orals, and the 

 evolution of pinnules. 



To turn to another passage and to a different group of animals. 

 At the bottom of page 197 ]\Ir. Hurst says : " In order to produce a 

 ' record,' it is necessary that new chapters be added at the end of the 

 pre-existing record. It is necessary that, as the adult structure varies 

 in one direction, the late stages of development shall vary in another, 

 so as to become, not more like the new adult structure than they were 

 before, but more like the old one." This is hardly a fair statement of 

 the case. It is not correct to say that the late stages of development 

 must vary in anothey direction ; for it surely is the case, in any series 

 of parents and offspring, which are varying in a given direction, and 

 which we may denote A^, A^, A^, A", that A^ is nearer to A? than As 

 is. Consequently, if the latest stage of development of the form A" 

 resembles A^, it is necessarily more like A~ than a stage which 

 resembled A^. That is to say, on the Recapitulation Theory, the 

 stages of development vary in the 5(7;;/^ direction as the adults. Mr. 

 Hurst's statement of the method of variation, demanded by the Re- 

 capitulation Theory, should, therefore, be amended as follows : — 

 Variation, or change from parent to offspring, takes place by the 

 addition of features at the end of the ontogeny ; and these features 

 are, by subsequent successive additions, gradually pushed back to 

 earlier stages of ontogeny, so that what is the ultimate stage of one 

 form is the penultimate of the next, and the ante-penultimate of the 

 next after that. 



Although the adherents of the Recapitulation Theory will doubt- 

 less accept the above as, in the main, a correct statement of the 



