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 



FIG. 109. Tiger swallowtail 

 butterfly, showing the two forms of 



diversity in 

 the same racial inheri- 

 tance. 



In many cases species 

 are not so sharply set 

 off from one another as 

 in the above example. 

 Often the characters are 



based on measurements. This is particularly the 

 case with birds and mammals. In such forms it 



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.) 



