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nomenclature which has been here adopted, with some necessary 

 changes. 



The dynamical relations of three great phases of evolution in the 

 phylum were designated by Haeckel * as the efiacme, including the 

 rise of the type from its origin, the acme, meaning the period of its 

 greatest expansion in members and forms, and the paracme, or de- 

 cline towards extinction, and these phenomena were correlated with 

 the similar physiological phenomena of the ontogeny, and these 

 appear in the table of phyletic terms given below. 



Previous to this, in the same volume (p. 76), Haeckel gives his 

 classification of the development of the individual under three 

 headings: "Anaplasis oder Aufbildung (evolutio)," meaning 

 thereby to include the physiological phenomena of all of the stages 

 developed in the four earlier stages of the individual. This is cer- 

 tainly a useful term for the entire series of transformations from the 

 fertilization of the ovum until the progressive stages are all passed 

 through. It does not express nor can it be used for cases of retro- 

 gression in which degenerative characters are introduced at such an 

 early age that progression is limited to the embryonic, or to that 

 stage and a part or the whole of the nepionic stage. There are 

 also some examples among parasites in which progression seems to 

 have been reduced so much that one can say it is practically elim- 

 inated from all stages succeeding some of the earliest embryonic. 

 For such forms as these the proper term would be Paraplasis, from 

 rtapa izXd<7<jw, meaning to change the form for the worse, to deform. 

 Thus the stages of such forms could be collectively spoken of as 

 paraplastic with relation to the ontogeny of others of their own type 

 or allied types, whereas they could not be described as anaplastic. 



The explanatory word "evolutio " is here used by Haeckel in a 

 confined and erroneous sense. Evolution really means continuity 

 in time invariably accompanied by change, but whether the modi- 

 fication be progressive or retrogressive, or a combination of pro- 

 gression and retrogression, is immaterial. It is obviously better not 

 to use these terms for ontogenic phenomena. There are sufficient 

 terms in "development," "differentiation of characteristics," 

 "rise," and one has always a slight mental reservation in employ- 

 ing this word for the growth and development of an individual or 

 isolated zoon. 



* Morphologic der Organismen, Vol. ii, pp. 320-366. 



