i$93-] / 9 [Hyatt. 
Either througli want of acquaintance with good exampk^s of 
retardation or because of a different point of view, I have not been 
able to see any duplex action in the law of acceleration. To me it 
is the same law of quicker inheritance which is acting all the time 
in the phylum at the beginning, middle, and end of its history, as 
will be seen by the explanations given above. In Insecta^ I have 
tried to apply it to the explanation of the pecuHar larval forms of 
be gathered from the text above, first, that I view acceleration, as a iiornial mode of 
action or tendency of heredity acting upon all characters that are genetic, or in other 
words derived from ancestral sources; secondly, that a ctetic or in other words newly 
acquired cliaracter must become genetic before it becomes subject to the law of 
tachygenesis. Haeckel has evidently confused ctetic characters like those of the 
so called ovum of Taenia, the pluteus of echinoderms, and the grub, maggot, and cater- 
pillar of insects, which have caused the young to deviate more or less from the 
normal line of development as determined by the more generalized development of 
allied types of the same divisions of the animal kingdom, with all normal characters 
that are inherited at an early stage in the ontogeny, and considers them all as 
heterochronic. It is very obvious that they are quite distinct, and while the ctetic 
characters may have been larval or even possibly embryonic in origin Hnd may not 
have affected perceptibly the adult stage at any time in the phylogeny of the group, 
they are, however, subject to the law of acceleration and do affect the earlier stages 
as has been shown in Hyatt and Arm's book on Insecta. Such characteristics do of 
course contradict the record if we consider that the record ought have been made by 
natai'e according to anthropomorphic standards and in this misleading phraseology 
they are falsifications of the ontogenetic recapitulation of the f)hylogeny. In a proper 
nomenclature, framed with due regard to natural standards sui;h expressions are 
inadmissible. There is absolutely no evidence that characteristics repeated in the 
younger stages of successive species and types owe their continuance in likeness to 
ancestral characters to other than heredity. This likeness may be interfered with or 
temporarily destroyed by extraordinary changes of habit as among the larvae of some 
Insecta and the forms alluded to above, or among parasites in different degrees, 
but the obvious gradations of the effects of these changes show that hereditary 
tendencies are not easily changed in this way. There are comparatively very few 
forms having doubtful affinities even among the parasites. It is also evident that 
tlie novel larval characters in their turn speedily become hereditary and are incorpo- 
rated in the phylogeny and recapitulated in the ontogeny. 
It may be seen from this that in dividing tachygenesis into palingenesis and ceno- 
genesis the writer has followed Cope rather than Haeckel and there is a serious 
objection to the use of cenogenesis at all since it is from kcvos meaning strange, and 
was tirst applied by Haeckel in such a way that both by his statements and the 
derivation it ought to be confined to types like larvae of theEchiuodermata, Insecta, etc., 
and parasites in which acquired characters do interfere with the ontogenic recapitu- 
lation for a certain time. Normal types in which tachygenesis occurs in a marked 
way might be called tachygenetic. Palingenesis and palingenetic might be confined 
to generalized forms in which the ontogeny was a more or less prolonged recapitulation 
of the phylogeny. This would avoid the need of using a new term. 
1 Guides for science teaching, Boston soc. nat. hist., no. 8 , 
