Hyatt.J 98 [April 5, 
tlio [loriocls of (Icvolopiiu'iit or only of tlie ])arageroiitic substnge 
in ontogeny may be spoken of and correctly described under this 
term . 
The use of "involutio" as a descriptive terra is objectionable, 
not only on the grounds given above, but because "involution" 
and '' volution" are both in common use as descriptive terms' for 
the peculiarities of the whorls of Gasteropoda and Cephalopoda. 
Any modification of evolution is objectionable because it is mis- 
leading. For example the word "/ivolution," supposed to mean 
things that do not evolve or have not been evolved, represents an 
unnatural condition. One can of course conceive of matter in a 
state of more or less stable equilibrium, but there are other words 
than "avolution" in habitual use to express this conception. It 
is also to be regretted that it has been applied by several eminent 
writers to ontogeny, and is probably fairly established in this 
application. The growth and development of the tissues is in a 
ger.eral way evolution, as much so as that of a colony of Protozoa. 
But it is also obvious that the product of the development by 
division of a single autotemnon, which forms a cycle, or when 
held together so as to form a colony, and the product of the 
division of an ovum in Metazoa held together more compactly so 
as to build up an individual or zoon, are not the same as the pro- 
duct of the evolution of an ancestor into a phylum through 
successive independent forms or ontogenic cycles. One cannot 
accurately speak of the •' growth " of a phylum, nor ought tlie word 
" development" to be used for the phylum. Development should 
be restricted to the zoon or individual or its morphic equivalent 
among Protozoa, since it expresses more clearly the differences 
that exist between ontogeny and phylogeny than their similarities, 
and for the same reason it is advantageous to use evolution for 
the phylum alone in the sense in which it is commonly employed. 
The necessity of subdividing the embryonic stage is admitted, 
and in all probability this really includes several stages with 
their own substages, but the discussion of this j^i'oblem must 
be left to the future. The former subdivision of the gerontic 
period into two parts also seems to have met with general 
acceptance, but the terms femain to be settled. Buckman and 
Bather have proposed catahatic to replace my old term " clin- 
ologic " taken from kWvw and Xo'-yos, which is an improvement, 
but their term "liypostrophic, " i>roposed from vTocrTpo<t>r' meaning 
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