Introduction. vii 



tion of orthogenetic and adaptative modifications have 

 led to various parallel series in this family is a subject of 

 philosophical interest too evident to be passed over 

 without comment; and if the interpretation of these 

 evolutionary series is at all sound, a step will have been 

 made in the advancement of our knowledge, and a more 

 rational basis laid down for the discussion of the probable 

 mode of geographical dispersion of the genera, species 

 and varieties. 



As in the past, I have been guided by broad views on 

 the conception of species, feeling that they are conducive 

 to a better understanding of the subject, to a truer 

 picture of the state of things in Nature. AVhilst not 

 losino* sio'ht of resemblances, I attach the fullest im- 

 portance to the recognition of minor forms or sub- 

 species, which I designate as varieties, in accordance 

 with the Linnean practice — there being no need to 

 depart from it. 



The material on which this monograph is based is, of 

 course, preserved mainly in the British Museum, to which 

 the important private collection of my fellow-worker and 

 adviser in the early days of my career, M. Fernand 

 Lataste, has been recently added through his friendship 

 and generosity. I have also utilized many specimens 

 lent to me by the late Dr. J. de Bedriaga, whose name 

 will ever be associated with the Lacertida3, Dr. F. Werner, 

 M. H. Gadeau de Kerville, Dr. L. Peringuey (South 

 African Museum), Dr. R. Gestro (Genoa Museum), Dr. 

 N. Annandale (Indian Museum), Miss Wilman (McGregor 

 Museum), Mr. A. Loveridge (Nairobi Museum), and Dr. 

 R. F. Scharff (Dublin Museum). Thanks to the kindness 

 of Prof. L. Roule and Dr. C. Gaillard, I have been able to 

 avail myself for study of the collections in the Paris and 

 Lyons Museums. 



The indications for the specimens in public or private 



