March 12, 1915] 



SCIENCE 



391 



suit either from a natural property of soil ni- 

 trogen or may be caused by denitrifieation of 

 soil nitrates usually caused by improper cul- 

 tural methods. 



K. F. Kelleeman 



SCIENTIFIC BOOKS 

 Water Reptiles of the Past and Present. By 



Samdel Wendell Williston, professor of 



paleontology in the University of Chicago. 



University of Chicago Press, 1914. Pp. 



vii -|- 251, with 131 text-figures. 



This interesting volume summarizes in a 

 most authoritative manner our knowledge of 

 the reptiles which have become adapted to 

 aquatic life, and it also includes a chapter on 

 the classification of reptiles, a subject upon 

 which Professor Williston, with his forty years 

 of special study, is abundantly fitted to speak. 



In his introduction the author speaks ear- 

 nestly in the defense of reptiles, which are so 

 often of ill repute as cold, gliding, treacherous 

 and venomous creatures shunning sunlight 

 and always ready to poison. As a matter of 

 fact, but few reptiles possess these evil pro- 

 pensities, for, aside from the venomous ser- 

 pents, there are but two poisonous reptiles 

 known, and the vast majority are not only 

 innocent of all offense toward man, but are 

 often useful to him. More than four thousand 

 reptiles are living, representing, however, but 

 four of the fifteen orders which were formerly 

 alive. The terse definition of a reptile as a 

 cold-blooded, backboned animal which breathes 

 air throughout life is not surely correct, since 

 it has been believed that certain extinct ones 

 may have been warm-blooded. 



While there are very marked distinctions of 

 structure between the amphibians and the rep- 

 tiles, there can be no doubt that the early 

 amphibian ancestors of the modern toads, 

 frogs and salamanders were also the ancestors 

 of all living and extinct reptiles. This is 

 proved by the fact that discoveries of recent 

 years have bridged over nearly all the essen- 

 tial differences between the two classes so com- 

 pletely that many forms can not be classified 

 unless one has their nearly complete skeletons. 

 In the case of some of the oldest amphibia, the 



Stegocephalians, we know that they were water- 

 breathers during part of their lives, because 

 distinct impressions of their gills have been 

 preserved, but we are not so sure that some 

 of the more highly developed kinds were not 

 air-breathers from the time they left the egg; 

 if this be true, our definition of a reptile as 

 distinct from an amphibian is rendered still 

 less secure. We are quite certain that from 

 some of the early extinct reptiles — ^probably 

 the immediate forebears of the great dinosaurs 

 — ^the class of birds arose, while another group 

 of primitive reptiles, called the Theriodontia, 

 and known chiefly from Africa, gave rise to 

 the mammals. 



The classification of reptiles is still a matter 

 of much doubt and uncertainty, no two authors 

 agreeing on the number of orders or the rank 

 of many forms. Many strange and unclassi- 

 fiable types which have come to light in Worth 

 America, South Africa and Europe have thrown 

 doubt on all previous classification schemes and 

 have weakened our faith in all attempts to 

 trace out the genealogies of the reptilian orders ; 

 and classification is merely genealogy. It is 

 only the paleontologist who is competent to ex- 

 press opinions concerning the larger principles 

 of classification of organisms and especially the 

 classification of reptiles. The neozoologist, 

 ignorant of extinct forms, can only hazard 

 guesses and conjectures as to the relationships 

 of the larger groups, for he has only the spe- 

 cialized or decadent remnants of past faunas 

 upon which to base his opinions. 



Williston's scheme of classification differs 

 only in minor details from the more conserva- 

 tive of the generally accepted views, and those 

 differences are, for the most part, the writer's 

 own opinions, to be taken for what they are 

 worth. It may be said decisively that no classi- 

 fication of the reptiles into major groups, into 

 superf amilies or subclasses that has so far been 

 proposed is worthy of acceptance; there is no 

 such subclass as the Diapsida or Synapsida, 

 for instance. 



Williston recognizes and briefly diagnoses 

 fifteen orders, of which three groups, the Pro- 

 ganosauria, Protorosauria and Thalattosauria, 

 are provisionally given this rank. 



