302 



GENERAL BIOLOGY 



form was considered a distinct species, on a " diag- 

 nostic " basis, and was given the name " glaucus." 

 When it was found, how- 

 ever, that eggs laid by 

 yellow females devel- 

 oped into both glaucus 

 and typical turnus, and, 

 conversely, that eggs laid 

 by glaucus developed 

 also into turnus, it be- 

 came necessary to con- 

 sider them one species. 

 The different forms 

 which are assumed by 

 those animal species in 

 which a marked alter- 

 nation of generation oc- 

 curs, and the different 

 types or castes of ants 

 and their relatives, are 

 further examples of mor- 

 phological diversity in 

 the same racial inheri- 

 tance. 



In many cases species 

 are not so sharply set 

 off from one another as 

 the above example. 



FIG. 109. - - Tiger swallowtail 

 butterfly, showing the two forms of 

 females : the upper one is the typical 

 "turnus," the lower one .is the "glau- 

 cus" type. The contrast is made 

 much more striking by the coloration, 

 which is yellow and black in the 

 turnus form and solid black in the 

 glaucus form. (From " Elements 

 of Biology," copyright, 1907, by 

 George William Hunter. Permission 

 of the American Book Co., pub- 

 lishers.) 



in 



Often the characters are 



based on measurements. This is particularly the 

 case with birds and mammals. In such forms it 



