EVOLUTION OF FOSSIL CEPHALOPODA. 233 
law has been rediscovered and renamed by Haeckel,* 
“das biogenetische Grundgesetz” and by Wiirtenber- 
ger.+ But these naturalists, instead of adding anything 
to Hyatt’s definition, have failed to reach its clearness 
and simplicity. The only real addition that has been 
made is Cope’s idea of retardation,{ by which is ex- 
plained the separation in the ontogeny of the descend- 
ant of characters that occurred simultaneously in the 
ancestor. Cope says: ‘The acceleration in the assump- 
tion of a character, progressing more rapidly than the 
same in another character, must soon produce, in a type 
whose stages were once the exact parallel of a perma- 
nent lower form, the condition of znexact parallelism. 
As all the more comprehensive groups present this re- 
lation to each other, we are compelled to believe that 
acceleration has been the principle of their successive 
evolution during the long ages of geologic time. Each 
type has, however, its day of supremacy and perfection 
of organism, and a retrogression in these respects has 
succeeded. This has no doubt followed a law the re- 
verse of acceleration, which has been called retardation. 
By the increasing slowness of the growth of the indi- 
viduals 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 paleon- 
* Morphologie der Organismen, vol. ii; and Anthropogenie, 
1874. 
{ Ausland, 1873, and Studien tiber die Stammesgeschichte der 
Ammoniten, 1880. 
t Origin of the Fittest. * Origin of the Fittest, p. 142. 
