Terms of Auxoloyy. — Buckman and Bather. 47 
of birth and puberty have no definite relation to particular 
stages in the above scheme, though they may accelerate or 
retard purely morphological characters. 
As a simple example of the ontogenetic stages, we may 
take the ammonite now known as Deroceras ziphus, of which 
some good figures were given by Wright under the name of 
Aegoceras dudressieri. Confining our attention to the sur- 
face characters, we see, following on the embryonic proto- 
conch, these stages : 
{ Brephic, Neanic, Ephebic, Gerontic / r .„ . 
. ' . . . . I his gerontic stage 
( Smooth. ( ostate. Spinous, ( ostate s 
i- clearly catahatic with reversion to neanic characters. It 
does not happen, in this species, to be succeeded by a hypos- 
trophic stage; but it is shown by closely allied species that the 
costate surface would be succeeded by a smooth one, that is 
to say, a reversion to the brephic stage so far as this charac- 
ter is concerned. 
On the other hand, in Coroniceras trigonatum Hyatt,* 
which is an individual of a retrogressive evolutionary series, 
the following auxologic changes may be noted: 
\ Brephic, Neanic, Ephebic, Gerontic / TT 
i a • n 4. ,< a .1 k • Here also the 
(Spinous, Costate, Costate, Smooth \ 
gerontic stage is catabatic ; but it is a reversion to a stage of 
phylogenetic development omitted from the ontogeny on ac- 
count of earlier inheritance. The same applies to the orna- 
mentation of both the neanic and ephebic stages. 
Phylogenetic Stages. 
It must be kept in mind that the terms hitherto considered 
denote stages in the growth of an individual. They or their 
predecessors have, however, often been applied, even by 
Hyatt himself, to stages in the history of a race. Beecher, 
though he points out the difference in clear enough language 
(op. cit. II, p. 148), nevertheless speaks of Gwynia and Cis- 
tella as nostologic (= hypostropliic) types of terebratu- 
loids; by which he means that in their ephebic stage they re- 
semble the earlier stages in the history of the group, or the 
brephic stages in the ontogeny of such a form as Terebratu- 
lina. This use of the same words for two very distinct ideas 
leads either to confusion of thought, or to the emplovmenl of 
^Genesis of Arietiche. Pi. vi, fig. 3; pi. vn, tig. 1, p. 1»U. 
