26 ACCELERATION OF DEVELOPMENT IN FOSSIL CEPHALOPODA 



of observers of fact. Along with speculations concerning the phylogeny 

 of the Ammonites there has been a much greater mass of painstaking 

 accurate systematic work, by which species have been carefully recorded, 

 variation and morphology studied most minutely, and a wealth of mate- 

 rial amassed for the use of the philosophic student of evolution. 



Conclusion. 



It may be that, when this paper is read by ardent members of the 

 "Hyatt school" of paleontologists and adherents of the biogenetic law, 

 they will be inclined to call the writer a deserter from the camp, and to 

 suggest that the paper ought to have been entitled, "Why recapitulation 

 does not recapitulate." The writer is still a firm believer in the bio- 

 genetic law, but that law is not such a simple thing as it was once thought 

 to be. In the youth of every theory everything is beautifully clear, and 

 ideally simple. As time goes on we are compelled to drop one idea after 

 another, until it almost seems that the whole will be lost. When sceptics 

 concerning the recapitulation theory throw up to us that ontogeny does 

 not always recapitulate phylogeny, we are prepared to admit this, even 

 to go further and admit that it does not often recapitulate. In fact, the 

 writer would be prepared to go still further, and to state that, in the 

 sense in which the term has been used by most adherents of the theory, 

 it never recapitulates. Our over-zealous friends have claimed too much, 

 and have done more to prevent general acceptance of the theory than 

 a host of enemies. 



