NATURAL SELECTION 289 



fact that Gredler has noted that in this area (if not in 

 exactly the same spot) are to be found ribbed Clausilias which 

 are obviously derived from smooth species (rossmassleri and 

 stenzii) . 



10. Linsdale (1928) has shown (with full statistical data) 

 that there is a correlation between certain osteological charac- 

 ters and the length of migration route in the Fox Sparrow 

 {Passerella iliaca). She treats the skeletal modifications as 

 adaptations to longer flight. But there is nothing to show 

 that they are not merely somatic modifications. 



1 1 . Chapin (in Linsdale, I.e.) records that the bills of various 

 species of Pyrenestes vary in shape and size, and that the varia- 

 tion is correlated with diversity of food. Linsdale {I.e. p. 360), 

 however, finds that the bill in Passerella exhibits marked racial 

 variation, though the food of the species is uniform. 



12. Annandale (1915) noticed that theoscula of the Sponge 

 Tetilla dactyloides var. differ from those of the typical form in 

 diameter, which he considers is due to their being adapted to 

 silt-laden water. This case is only generally stated. 



13. Pickford (1926) states that in moist soils it is customary 

 to find ' superpapillate ' forms of various species of earth- 

 worms. This is supposed to be an adaptation necessitated by 

 locomotion over slippery soil. The facts are not presented 

 very fully, and there are no figures showing the incidence of 

 the various types on various soils. 



14. Colour-pattern in lizards of the genus Cnemidophorus 

 {Gadow, 1903). 



Gadow studied the colour-pattern of these Central American 

 lizards, which seems to display an orthogenetic development 

 analogous to that observed in the Mediterranean Wall Lizard 

 by Eimer (1881). He found the same tendency for a pattern 

 theme to pass through various similar stages in allied species. 

 He claims that in some cases it is possible to relate the various 

 stages in the modification of the pattern, of which the essential 

 feature is the break-up of a primitive series of stripes into spots 

 which are ultimately assembled into transverse bands, to the 

 habitat occupied by the various species and subspecies. Thus 

 in sandy terrain with moderate vegetation he found C. guttatus 



u 



