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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 
