401 
the nepionic stages. The earlier characteristics of the ontogeny 
are, as the author has striven to explain in several publications, 
essentially distinct, being in large part in most animals and in some 
cases almost wholly genetic. In considering the simplest manifes- 
tations of the cycle, palingenesis accompanied always by tachygen- 
esis must be taken into account, and also cenogenesis in groups like 
Lepidoptera, Hymenoptera, most Echinodermata, many Vermes, 
where a supposed ancient and regular palingenetic record is assumed 
to have been disturbed by ctetic characters acquired by the larvee.* 
The gerontic characters, on the other hand, and all paraplastic, 
as well as their corresponding phyloparaplastic characters belong to 
the category of analogies in so far as they are purely morphic 
resemblances or equivalents. This is clearly shown in the physiology 
of all the parts and organs in the anaplastic and paraplastic periods, 
the former being full of hereditary and perhaps, also, acquired 
power, and the latter more or less weakened and reduced or worn 
out by the exercise of those powers and the constant wear and tear 
of the surroundings. 
Retrogressive reductions in every form, although often indicating 
and accompanying a high degree of specialization, partake more or 
less of the same nature when considered with reference to their 
morphic and accompanying functional attributes, and one cannot 
study such bioplastic phenomena as if they were of the same nature 
and subject to exactly the same laws as progressive genetic and 
ctetic characters. As I have pointed out above, and in several 
other publications, there are all degrees of completeness in the 
evolution of the cycle, and it is dependent upon a variety of causes 
whether occurring in the ontogeny or phylogeny. If it were con- 
stant and invariable and independent of the surroundings in the 
* Such examples are, correctly speaking, not disarrangements of palingenesis, although 
so translated by Haeckel, if I rightly understand his ideas of a confused record. Ceno- 
genism does occur in such examples in obedience to the same law that governs palin- 
genesis, but it occurs through the introduction of ctetic characters during the larval 
instead of in the neanic or ephebic stages, and the crowding back of these upon the 
nepionic and embryonic stages. The use of terms indicating that nature has confused 
or destroyed its own ontogenic records of the transmission of characters in certain cases 
assumes (1) that these are exceptional cases, (2) that cenogenesis is not the normal mode 
of transmission in certain types in which it occurs, (8) that both of these modes of trans- 
mission are not affected by tachygenesis, all of these implications being erroneous 
according to the opinions expressed above. One can assume a disturbance or perturba- 
tion, or decided change of mode according to law, but ‘‘ destruction,’’ ‘‘ confusion,” or 
‘‘ falsification’’ are subjective terms inapplicable to the objective character of the phe- 
nomena to which they are applied, appropriate in metaphysics, perhaps, but entirely 
out of place in natural science. 
PROC. AMER. PHILOS. SOC. XXXII. 148. 2Y. PRINTED JUNE 6, 1894. 
