1893. RAE RECAPITULARION THEORY. 
279 
third the adult of each species. In none of these is the embryonic 
stage given, since it varies very little, being of the same smooth 
character throughout. It becomes, therefore, interesting to learn 
how Mr. Hurst explains the tuberculate infantine stage of C. trigo- 
natum, which is certainly considerably less like its own adult than 
is the corresponding stage of C. lyva; it cannot possibly be 
explained as an attempt of the embryo to become like the adult. 
Indeed the whole table, the facts of which are given in full detail in 
Hyatt’s monograph, and the main principle of which is maintained 
by two independent workers, is totally opposed to all Mr. Hurst's 
contentions. 
It should also be remembered that there are many 
details of structure, too complicated to be dwelt on here, but all con- 
firming the other evidence. 
Coroniceras trigona- 
tum 
C. gmuendense 
CIO Bal Bo Feo 

GATatiforme ..1  ..-+ 
| 
GiiRrtdtoyece se eee 
| 
Semicos- | 
l 
Aynioceras 
tatum 
A, miserabile. 
INFANTINE. 
Well-marked ribs and 
slight tubercles. 
Quadrate section. 
Keel? 
Well-marked ribs and 
slight tubercles. 
) Subquadrate section. 
Slight keel. 
Ribs and slight 
tubercles. 
Broad subquadrate sec- 
tion. 
Slight keel. 
Smooth, and then slight 
ribs. 
Roundish section. 
Very slight keel. 
Almost smooth. 
Broad rounded section. 
No keel. 
Smooth. 
Roundish section. 
No keel. 
Smooth. 
Round section. 
No keel. 
ADOLESCENT. 
Broad ribs. 
Section unknown. 
Slight keel. 
Clear ribs and 
tubercles. 
Compressed quadrate. 
Keel. 
Ribs and tubercles. 
slight 
Subquadrate section. 
Slight keel. : 
Ribs and tubercles. 
Broad subquadrate. 
Slight keel. 
Slight ribs. 
Broad subquadrate sec- 
tion. 
Slight keel. 
Smoothand slight folds. 
Elliptical section. 
Trace of keel. 
Smooth. 
Slightly compressed 
round section. 
No keel. 
ADULT. 
Nearly smooth. 
Subtriangular section. 
Very slight keel. 
Slight ribs. 
Compressed quadrate. 
Pronounced keel. 
Tubercles. 
Slightly compressed 
subquadrate section. 
Keel. 
Pronounced tubercles. 
Subquadrate section. 
Keel. 
Tubercles. 
Subquadrate section. 
Keel. 
Slight ribs. 
Slightly broader section. 
Slight keel. 
Smooth. 
Elliptical section. 
Slight keel. 
Professor Huxley once said that if Evolution had not already 
been an accepted theory, the paleontologists would have had to have 
invented it. It might, with no less truth, be asserted that, if the 
embryologists had not forestalled them, the palzontologists would 
have had to invent the theory of Recapitulation. As a matter of fact, 
many of them seem actually to have arrived at it quite independently 
either of one another or of the neontologists, a circumstance that 
does not necessarily prove the truth of the theory, but that should, 
at least, have led Mr. Hurst to pay some attention to their opinions. 
With evidence such as has just been quoted before them, it would, 
indeed, have been difficult to have arrived at other conclusions ; at 
the same time, it must not be supposed that all lines of descent, even 
among Ammonites, show the facts with equal clearness. There are, 
as has already been hinted, many modifying forces at work, and the 
chief of these may be conveniently included under the one head of 
economy. ‘To this is due the disappearance from the record of those 
features that are not adapted to the needs of the animal in the early 
