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conjugation with other broods took place whenever it was permitted 

 by the experimenter. 



In the generations immediately succeeding these, degenerative 

 changes, both structural and physiological, took place in the parti- 

 tions which were distinctly paraplastic, although the cultures were 

 maintained under conditions which precluded the supposition that 

 these changes could have resulted from unfavorable, abnormal sur- 

 roundings. The successive partitions then had gerontic transforma- 

 tions, lost their micronuclei, became much reduced in size and 

 unable to conjugate with others with the usual normal results, and 

 finally the external buccal apparatus was affected, reduced, or oblit- 

 erated, and so on. These changes were termed senile by Maupas, 

 who explains the entire phenomena as a cycle comparable with that 

 of the individual among Metazoa. 



One is, of course, at this incipient stage of bioplastology, con- 

 fused by many apparently inexplicable phenomena. When, how- 

 ever, one contemplates the confusion of the most eminent authori- 

 ties with regard to the relations of the autotemnon among Protozoa 

 and Metazoa, shown by the use of the same term for the autotem- 

 non, the individual, and the zoon, and also the prevalent confusion 

 with relation to the morphology of forms designated as colonies — 

 some regarding the whole product of one egg as an individual and 

 others considering each bud or independent zooid as properly des- 

 ignated by that term and defining the colony as an aggregate of 

 more or less connected individuals — it is surprising that there 

 should not be more difficulties in the path of this new branch of 

 research. 



Those who try to find the cycle of metamorphoses in their own 

 special branches of research will be often disappointed and probably 

 deny that it exists at all. Thus, in my own case, I for some time 

 could not find any evidence of its existence among certain cephalo- 

 pods, notably those having a primitive organization like Endoceras 

 and Orthoceras ; but I have since seen well-marked senile stages in 

 these shells. Undoubtedly there is as great distinction between 

 the paraplastic and anaplastic periods, and between phyloparaplasis 

 and phylanaplasis everywhere, as there is between the correlations 

 of the corresponding periods at the extremes of the ontogeny and 

 phylogeny. 



Paraplasis essentially differs from anaplasis, as has been described 

 above in treating of relations of analogy between the gerontic and 



