Hyatt.] 11^ [Aprils, 
obliterated, and so on. Tliese cliaiio-os were tCM'ined senile by 
jMaupas, who explains the entire phenomena as a cycle coini)ar- 
able with that of tlie individual among JNIetazoa. 
One is of course at this incipient stage of bioplastology confused 
by many apparent!}' inex|)lical)le phenomena. AVhen it is remem- 
bered, however, the confusion of the most eminent authorities 
with regard to the relations of the autotemnon among Protozoa 
and jNIetazoa, shown l)y the use of the same term for the auto- 
temnon, the individual, and the zoon, and also the prevalent con- 
fusion with relation to the morphology of forms desiguated as 
colonies, some regarding the whole ])roduct of one egg as an 
individual and others considering each bud or independent zooid 
as projierl}' designated hj that term and defining the colony as a 
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 C3'cle of metamorphoses in their own 
special branches of research will be often disappointed and prob- 
ably 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 cephalopods, notably those having a primitive organiza- 
tion like Endoceras and Orthoceras ; but I liave since seen well 
marked senile stages in these shells. Undoubtedly there is as 
great distinction between the paraplastic and anaplastic periods, 
and between phylo[»araplasis and jihylanaplasis 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 the nepionic stages. The earlier characteristics of 
ontogeny are, as the author has striven to explain in several 
publications, essentially distinct, being in large part in most 
animals and in some eases almost wholly genetic. In considering 
the simplest manifestations of the cycle, jialingenesis accom- 
panied always by tachygenesis must be taken into account and 
also cenogenesis in groups like Lepidoj^tera, Hymenoptera, 
most Echinodermata, many yernies, where a sujjposed ancient 
