HYATT. — ORGANIC CYCLES. 219 



tioii by addition of new structures or characteristics based on older struc- 

 tures and thus leading to greater and greater complication of the primitive 

 organization. The acme represents the time of greatest complication in 

 structure and greatest expansion in numbers of forms for any group, 

 large or small. The paracme is the decline, and this takes place througii 

 the reduction and actual loss of structures and characteristics that have 

 been built up by evolution during the epacme. This is no ideal picture, 

 but a simple statement of the experiences of those paleontologists who 

 have patiently traced the history of groups through geologic time. 

 Agassiz's law enables one to follow the epacme of the evolution of a 

 species, or genus, or order, or larger group, but further correlations be- 

 tween the cycle of individual life and those in the evolution of its own 

 genetic group must be sought in the correlations existing between the 

 older retrogressive stages of the ontogeny and the paracme of each 

 group. 



The importance and peculiar nature of these correlations led me, in 

 one of my papers, to introduce, for this branch of research, the term 

 * Bioplastology,' which will be found convenient by those interested 

 in this class of work. 



The following table of terms is useful here to explain the relations of 

 the cycle of development in the individual to that of the group to which 

 it belongs. 



Terms of Bioplastology explaining the Correlations between Stages 

 OF the Ontogeny and those of Phylogeny. 



Ontogeny or Development. Phijlogenij or Evolution of the Phylum. 



Structural «!fn„oo Structural „, t^ • , 



Conditions. ^*^Ses. Conditions. S*^Ses. Dynamical. 



I Embryonic Embryo or Foetal I Phylembrvonic 



Anaplasis j Nepionic Baby Phylanaplasi.s \ Phy lonepionic Epacme 



( Neanic Adolescent ( Pliyloneanic 



Metaplasis Ephebic Adult Phylometaplasis Phylephebic Acme 



Paraplasis Gerontic Senile Phyloparaplasis Phylogerontic Taracme 



The dynamical terms are quoted from Haeckel, and were used by him 

 to designate the phenomena of the rise and decline of types, and also the 

 terms anaplasis and metaplasis. He, however, used ' cataplasis ' in 

 place of paraplasis, which is here preferred on account of the faulty deri- 

 vation of cataplasis. 



He realized the importance of these phenomena, and also the signifi- 

 cance of the structural characteristics of decline, but did not trace out 

 the distinct correlations which are claimed as fundamentals in bioplas- 

 tology. 



