ARE SPECIES REAL ? 79 



Studies of Darwin. Animals of the Galapagos Isl- 

 ands ; persistence of edentates in South America. 



Types persist through space and through time. 

 Species change with either space or time. With time, 

 because time gives rise to events which cause diverg- 

 ence. All divergence really dichotomous. With space, 

 because with space come barriers which again pro- 

 duce dichotomous divergence, in both cases followed 

 by isolation and segregation of characters. 



Study of small variations in species. Methods of 

 Professor Baird. Pacific railroad survey (1856-8). 

 Mexican boundary survey. 



Studies of Dr. Joel A. Allen (Mammals and Winter 

 Birds of Florida). Species and sub-species. Known 

 presence of intermediate forms sole test of validity of 

 species. 



Illustration : Shore-lark, Otocoru alpestris, and its 

 varieties : praticola, leucol&ma, arenicola, giraudi, me- 

 nilli, chrysolfzma, adusta, slrigata, rubea, pallida. 



Song sparrow, Melospiza fasciata, and its varieties. 



Bluebird, Sialia sialis,aretica,8ind mexicana, distinct 

 species. 



Meadow lark, Sturnella magna and neglecta, doubt- 

 ful species. 



Flicker, Colaptes auratus and cajer, doubtful species. 



My own experience with species. 



The trout ; Salmo gairdneri, the steel-head ; Salmo 

 irideus, the rainbow trout ; Salmo mykiss, the " cut- 

 throat trout," and its varieties : lewisi, in the Mis- 

 souri ; stomias, in the Platte and Arkansas ; mac- 

 donaldi, in the Twin Lakes ; spilurus. in the Rio 

 Grande ; pleuriticus, in Utah Basin ; henshawi, in 



