THEORY OP RADICALS \M> MORPHOLOGICAL EQUIVALENCE. 'Jl 



the life of an individual, and in accordance with these ideas designated the pro- 

 re periods of expansion in the phylogenetic historj of a group aa the 

 Epacme, the period cpansion in Dumber and variety of species and 



forma as the Acme, and the periods of lecline in uumbers of >[■ aa the 



me. 

 Haeckel used also the term Anaplastologj for tli" physiological relatioi 



th and those of the epacme "i groups, Metaplas- 

 -■■ of the adult and tin* acme of groups, and Cataplastologj for 



tho f the senile Btagea and the paracme of groups. These terms seem to 



ind aa those we bave employed, but they were in reality 

 n for the p ying; physiological relations. Thus the anaplastic 



oris of tin- naepionic and nealo - to the phenomena occurring dur- 



ing the epacme ■ -. the metaplastic relations of the ephebolic stages to the 



phenomena occurring at the acme of groups, and the cataplastic relations of the 

 the phenomena occurring during the paracme of groups, are 

 tin- functional relatione of the structural modifications occurring in the ontogenj 

 of individuals :■» those which are characteristic of the phylogeny of gro 



Theory o*f Radicals \m> Morphological Equivalent in 

 Progressive Forms. 



The simpler characters of the BUturea in the adults of more ancient forms, aa 

 compared with the more modern Bpeciea <>i' the same Beries, has been noticed by 

 Zittel, Neumnyr, Waagen, and Branco, 1 in different groups of 

 A 1 1 1 1 1 1 <> 1 1 i t i 1 1 : i • . The first is verj decided in bis statement, thai the AmmonitinoB 

 be lia> studied form perpetually diverging Beries, which spring from certain 

 common ancestral forms. 



constant repetition of discoidal and involute forma in series, which are 

 otherwise distinct in respect to their Butures and minor characteristics of develop- 

 ed shell markings, produces a similarity in the bu< of the forma 1' 

 i compare the evolution of discoidal ini>> more involute fori 

 any oi with a similar genetic procession in any other Beries. Thus in the 

 1 ; rnmary, Plate XI\ . we can compare the discoidal forms of Per. I 

 20, with A I ' I " l / 



ime way the involute forma of Ast. ( 

 i , : / I these i omparisona also hold ^ « >< » « 1 for 



/.' ind tin- terminal forma like Wah. E 



which I series tin- whorls do not become more 



••• in tin- h b it are ni ■ modified in those chan 



ipany and ciirnd.it.' with increase of involution. Thus 

 iteral diameter oi tin- whorl ome more and 



■ 



w 



\ ii 



