tti Tin American Geologist. July, 1898 
■1 Brephic stage immediately succeeds the embryonic, and 
during it no specific characters can be distinguished. 
:} Neanic. During this stage specific characters and all 
other morphological features present in t In* adult, appear and 
undergo development. 
4 Ephebic stage denotes the period of full development of 
the individual, when all specific characters are clearly rec- 
ognisable. 
5 Gerontic. During this stage changes take plaee which 
are due to gradual failure of powers. The stage may be 
sub-divided into : 
a Catabatic stage, in which the individual loses its ephebic 
characters. 
b Hypostrophic stage, in which the continued loss of char- 
acters causes pronounced reversion. 
Examples and Remakes. 
It may be noted that in an individual of a progressive 
series gerontic changes are truly reversionary, the decline 
due to diminishing vitality in the catabatic stage causing a 
certain degree of reversion to the characters of the neanic 
stage. In an individual of a retrogressive series, however, in 
which the characters of the ephebic stage are less elaborate 
in development than those of the neanic. or even brephic 
stages, the gerontic stages shew simply characters of a still 
further decline. In some extreme cases, however, the hypo- 
strophic stage of an individual of a retrogressive series may 
possess characters of. apparently, a renewed progressive de- 
velopment: from which it would seem that when reversion 
has completed the cycle of changes, further reversion may 
produce characters belonging to a recommencement of the 
cycle. 
In applying the definitions of the brephic and neanic 
stages, it should he remembered that specific characters 
sometimes make their appearance in ontogeny before generic. 
The period at which any character appears depends largely 
on the length of time for which it has been a character of 
the race. In many cases, characters that are regarded as 
specific have a higher antiquity than those that are regarded 
as generic. 
It may also he pointed out that the physiological episodes 
