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creasing complexity of the development and its decline, the ana- 

 plasis, metaplasis and paraplasis of the individual ; or one may- 

 describe the cycle as exhibited by the embryonic, nepionic, neanic, 

 ephebic and gerontic stages, or the cycle of thephylogeny as exhib- 

 ited by the corresponding phylostages * of evolution designated by 

 their appropriate prefix "phyl." 



There appears to be real need of two terms under the head of 

 cycle, one for ontogeny and the other for phylogeny. It is proposed 

 to use in this way ontocycle or ontocyclon for the ontogeny, mean- 

 ing the cycle of the individual, and phylocycle or phylocyclon for 

 that of the phylum. This will make it practicable to use the terms 

 monocyclon or monocyclic, polycyclon or polycyclic, etc., to de- 

 scribe the number of cycles observed. Thus the ammonoids are 

 polycyclic, the Arietidae are decacyclic, the genus Coroniceras is an 

 incomplete monocycle. 



It is not necessary to defend these terms before students of bio- 

 plastology ; they will be tested, and, if convenient, adopted. For 

 the benefit of others it may be mentioned that the cycle is of all 

 degrees of development in ontogeny. Thus, Insecta are apt to stop 

 at the ephebic stage and in many other animals there is a similar 

 limitation. On the other hand, there may be the most unexpected 

 development of the cycle. Thus, Podocoryne starting from the hy- 

 droid stage passes through a permanent colonial stage built up by 

 budding which gives rise by secondary buds to independent medusae. 

 The life of an independent medusoid bud ends with a paragerontic 

 substage in which the veil is destroyed, the bell is partially re- 

 sorbed and turned back together with the tentacles, and the pro- 

 boscis is left naked and projecting. In this condition the old of 

 Podocoryne is similar to the hydroid with which the colony began. 

 This gerontic transformation has been observed by Dujardin in 

 Cladonema and Syncoryne, by Hincks in Podocoryne and Syn- 

 coryne, and by Gosse in Turris.f 



Man is not completely ontocyclic, but makes a close approach to 

 this in the loss of the hair, teeth and proportions and shape of the 

 body ; and certainly in some parts, as in the mandible described 

 above, there is sometimes a completed cycle. 



* This word is a fearful hybrid, and I beg pardon of my classical friends in advance of 

 their merited wrath. 



f Dujardin, Ann. Sci. Nat, Series 3, Vol. iv, pp. 257-231, 1815; Hincks, British Hydroid 

 Zoophytes, Vol. i, p. xxviii, 186S. 



