-GEOLOGY 



77 



Indeed, Rhumbler in summing up his own conclusions says, ' We see 

 therefore that the adult stage is just as good for generating new structures 

 as is the embryonal end of the shell.' This can hardly be regarded as 

 giving strong support to the principle of protcrogenesis. 



I do not propose to discuss his references to evidence drawn from 

 human development, for we cannot hope to understand the principles 

 which govern the development of such highly complex organisms as 

 man until we have straightened out some of the tangle in which our 

 ideas of the development and evolution of simpler forms have become 

 involved. 



5 



c 

 w 



o 



Cyclolituites. 



Ancistroceras. Lituites. 



rare 



Rhynchorthoceras. 



Fig. 3. — Diagram showing the distribution in time and the development of some 

 representatives of the nautUoid family Litnitdce. (Modified from Schindewolf .) 



From time to time over a period of years Spath has made references 

 to examples illustrative of the principle under discussion. They have, 

 however, usually been buried in a mass of systematic detail that has made 

 it difficult for others to extract who have not his unrivalled knowledge of 

 a great multitude of ammonites. For this reason we look forward to 

 the publication of his Catalogue of the Liparoceratidce in which he 

 has incorporated his evidence and views in a more accessible form. 

 Meanwhile he has indicated the lines of his evidence in a recent paper 

 (1936) and has done me the great kindness of giving me a personal 

 demonstration with the help of a typical suite of specimens, and thus 

 enabled me to give the following brief summary. 



Dr. Spath claims that the various members of this family arose out 

 of a stable stock of forms referable to the genus Liparoceras, which ranges 



