882 Values of the Stages of Growth and Decline. 
Heckel used also the term Anaplastology for the physiological 
relations of the stages of progressive growth and those of the Epacme 
of groups, Metaplastology for those of the adult and the Acme of 
groups, and Cataplastology for those of the senile stages and the 
Paracme of group. These terms seem to cover the same ground, 
as those we have employed, but they were in reality chosen for the 
purpose of classifying physiological relations. Thus the anaplastic 
relations of the Embryologic, Silphologic and Nealogic stages to the 
phenomena occurring in the Epacme of groups, and the metaplastic 
relations of the Ephebolic stages to the phenomena occurring at the 
Acme of groups, and the cataplastic relations of the Geratologic 
stages to the phenomena occurring during the Paracme of groups, 
are the functional relations of one class of morphological modifi- 
cations to those of another class and do not properly include the 
morphological phenomena themselves or their morphological 
correlations. 
The necessity for a double set of terms may possibly not be at first 
admitted by many zoologists on account of their too exclusive devo- 
tion to the morphological side of their studies, but a very slight — 
experience in trying to express the serial correlations of morpholo- 
gical and physiological phenomena will very soon show them, the 
convenience of such a nomenclature. Geologists have already 
arrived at this conclusion with regard to the classification of strata 
in the earth’s crust and have begun to use two parallel series of 
terms, one giving the nomenclature of the relations in time, Era, 
Period, Age, etc., and the other the faunal relations under the 
headings of Group, System, Stage, and so on. The time has come 
for recognizing a similar parallelism between structural or statical 
phenomena of organisms and their dynamical or physiological 
relations in time, and it is necessary to separate these clearly by 
different series of terms in order to see not only how they are 
separable, but also their correlations. Te 
We have been more or less constantly observing and publishing 
on the Geratologic stages among fossil Cephalopoda for more than 
twenty years and have repeatedly described the more or less exact 
comparisons, which can be made between the different stages of de- 
cline in the individual and the degraded forms occurring in the oaiae 
group. 
1G. K. Gilbert, Address, Am. Ass. Adv. Sci., 1887. 
