Geology and Natural History. 119 



but could not have formed any such frill as that of Dimetronod 

 or the basilisk lizard. 



The authors go on to say: 



"And this structure of the vertebra has an important bearing in 

 any discussion as to the meaning of the spines in Dimetrodon. 

 That Dlmetrodon could have developed such extraordinary spines 

 without affecting to a great degree the characters of the skeleton 

 proves conclusively their relative physiological unimportance.* 

 Certainly, had the enormous dorsal expansion of Dimetrodon been 

 of profound importance in the life economy of these creatures, it 

 must have materially affected the structure of the skeleton else- 

 where. That iSphenacodon is more primitive than Dimetrodon 

 must be admitted to be perhaps another bit of evidence of the 

 greater antiquity of the New Mexico deposits than the upper 

 ones, at least, of Texas" (p. 69). 



The last chapter, by Williston and Case, describes Edapho- 

 sdurus Cope, with a new species, E. novomexicamts. The type 

 skull, although somewhat fragmentary, " is of importance as fur- 

 nishing for^the first time indubitable evidence of the relationship 

 of Edaphosaurus and Naosaurus^ whereas the " relationships of 

 Edaphosaurus and Dimetrodon, notwithstanding the similarity of 

 their dorsal spines, cannot be very intimate. The conclusion is 

 irresistible that these resemblances were, for the most part at 

 least, merely the result of convergent evolution." r s. l. 



10. The Meaning of Evolution • by Samuel C. Schmucker. 

 Pp. 1-298 ; with frontispiece and 7 illustrations. New York, 

 1913 (The Macmillan Company). — This book fulfils the author's 

 purpose, that of presenting a simple, readable statement so that 

 the " average person " having no special training in the sciences 

 may be brought to an understanding of the doctrine of evolution. 



Chapter I is an historical summary of the development of the 

 evolutionary idea from the time of the earliest writer, Anaximan- 

 der, 600 B. C, until the coming of Darwin. The following 

 chapter sets forth the never-to-be-forgotten career of Darwin, the 

 co-discovery of the idea of natural selection by Darwin and Wal- 

 lace and the rare example of scientific chivalry these men gave 

 the world. Chapter III treats of the underlying idea of evolution, 

 laying special emphasis upon the four basic conceptions of hered- 

 ity, variation, multiplication, and selection. The next two chap- 

 ters deal with adaptation, — one with that of the individual in 

 clothing, color, protective attitudes, weapons, and so on, and the 

 other that of the species, especially in the features wherein the 

 contrast of the sexes lies. The author, while realizing the doubt 



* "Case would hesitate to endorse the statement that these elongated spines 

 were physiologically unimportant. He has long considered (and frequently 

 stated his belief) that the enormous development of the spines in Dimetrodon 

 and probably also in Edaphosaurus (Naosaurus), imposed upon the creatures 

 a physiological burden so great in its demands upon the energies of the indi- 

 vidual, both for their original production and the repair of frequent injuries, 

 that it was an important, if not the chief, cause of their extinction." 



