510 SIL GLOIOE SS I MONS SSI GIOY PIM TOS 
a law the reverse of acceleration, which has been called vetarda- 
tion. By the increasing slowness of the growth of the individ- 
uals of a genus, and later and later assumption of the characters 
of the latter, they would be successively lost. 
By a proper application of the law of acceleration as defined 
by Hyatt, and modified by Cope, all the facts of biology may be 
explained; there is no such thing as “‘ falsification of the record.” 
But as yet the law has had no great effect in classification, for 
most paleontologists have not approached their work from the 
biologic side, and biologists have been equally neglectful of the 
results attained by paleontology. A distinguished zodlogist once 
said to the writer, on being shown an ontogenetic series of 
ammonites, and the conclusions reached, ‘‘It is all beautiful, but 
almost too good to be true.” In paleontology it is especially 
true that a naturalist may be a specialist in the fauna of one age, 
and know little of that of another. Hence the animals of various 
periods have been classified according to varying standards, all 
artificial, The only cure for these discrepancies is study of 
ontogeny, and comparison of stages of growth of the individual 
yy 
with ancestral genera. This will also prevent the description of 
supposedly new genera and species based on immature specimens, 
as has so often been done. The writer remembers once collect- 
ing numerous Ceradites in the Karnic limestone of the California 
Trias, much to his astonishment, for they ought not to occur so 
high up. He afterwards found, however, that they were not 
adults, but adolescent ceratitic stages of Avpadites ; a similar 
case was the finding in the same horizon a 7zrolites above its 
proper range, but it turned out to be the young of a Tvachyceras 
that persisted unusually long inthe 77zvolites stage. At that time 
there was nothing in the description of these genera or any of 
their species to guide one, and so their ontogeny had to be worked 
out independently. But there is nothing in the description of 
almost any fossil genera and species to prevent just such mis- 
takes, and they are constantly being made. 
By careful study of ontogeny in comparison with phylogeny 
* Origin of the Fittest, p. 142. 
