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" !Metaplasis oder Umbildung (transvolutio)" is used by the same 

 eminent authority for the adult period in a general sense, and it 

 appears to the writer to have useful function as a descriptive term 

 especially, since it is uniform with anaplasis and paraplasis. Thus 

 one can describe the metaplastic phenomena or characteristics of 

 the ephebic stage in any form as metaplasis, and also speak of the 

 general meaning of metaplasis without referring to that stage of 

 ontogeny in any special form. The use of "transvolutio" is 

 obviously objectionable, since it introduces confusion and conflicts 

 with the proper definition of " evolutio " or evolution as given 

 above. 



" Cataplasis oder Riickbildung(involutio)," used by Haeckel for 

 the senile stage, is open to the objection that there is no correspond- 

 ing Greek word, and also that y.axa-ld<jao), the only Greek verb to 

 which this term can be referred, means to spread over or plaster. 

 Paraplasis, derived from -apa -Xdaaw, meaning to change the form 

 for the worse or deform, is an obviously preferable designation. 

 Thus the paraplasis or paraplastic phenomena of all the periods of 

 development or only of the paragerontic substage in ontogeny may 

 be spoken of and correctly described under this term. 



The use of " involutio " as a descriptive term 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 mislead- 

 ing. For example, the word "avolution," 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 appli- 

 cation. The growth and development of the tissues is in a general 

 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 individ- 

 ual or zoon, are not the same as the product of the evolution of an 

 ancestor into a phylum through successive independent forms or 



