1893- 



THE RECAPITULATION THEORY. 



279 



third the adult of each species. In none of these is the embryonic 

 stage given, since it varies very httle, 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. lyra : 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. 



1 Well-marked ribs and 

 slight tubercles. 

 Quadrate section. 

 Keel ? 



/Well-marked ribs and 

 I slight tubercles. 

 ■■' 1 Subquadiate section. 

 I Slight keel. 



/Ribs and slight 

 tubercles. 

 ... - Broad subquadrate sec- 

 tion. 



V Slight keel. 



/ Smooth, and then slight 

 1 ribs. 

 ■■■ "j Roundish section. 

 I Very slight keel. 



I Almost smooth. 



1 Broad rounded section. 



vNo keel. 



Smooth. 



Roundish section. 

 No keel. 



Adolescent. 

 Broad ribs. 



Adult. 

 Nearly smooth. 



C gmuendense 



C. lyra 



C. rotiforine 



C. kridion... 



A rnioceras 

 tattitn 



Section unknown. 

 Slight keel. 



Clear ribs and slight Slight ribs 



tubercles. 

 Compressed quadrate 

 Keel. 



Subtriangular section. 

 Very slight keel. 



A. miserabile. 



[ Smooth. 



) Round section. 



No keel. 



Ribs and tubercles. 



Subquadrate section. 



Slight keel. 



Ribs and tubercles. 



Broad subquadrate. 

 slight keel. 



Slight ribs. 



Broad subquadrate sec- 

 tion. 

 Slight keel. 



Smooth and slight folds. 

 Elliptical section. 

 Trace of keel. 



Smooth. 



Slightly compressed 



round section. 

 No keel. 



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 palaeontologists would have had to have 

 invented it. It might, with no less truth, be asserted that, if the 

 embryologists had not forestalled them, the palaeontologists 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 



