226 EVOLUTION OF TO-DAY. 



this admission on Darwin's part, his original theory 

 has become so much modified that it is no longer 

 simply natural selection. The fundamental cause 

 in the change in species is something which pro- 

 duces simultaneous variations. Upon these varia- 

 tions natural selection may act, but it is secondary, 

 the primal fact being the law or laws which produce 

 simultaneous variations in many individuals. 



It must, however, be noticed that observation 

 teaches that crosses between two varieties do not 

 always produce intermediate varieties ; sometimes 

 the offspring show all of the features of one parent. 

 When the Ancon ram is crossed with the female of 

 an ordinary breed, the young are of the Ancon va- 

 riety, and not an intermediate form. 



Development of Organs by Small Steps. 



Not only has the necessity of simultaneous varia- 

 tions been clearly shown, but it seems equally 

 evident that some of these variations must be of 

 considerable importance. Many organs can hardly 

 be explained as being developed by small steps, 

 such as those of which natural selection is supposed 

 to make use. In the first place, it is impossible to 

 understand how certain organs could have origi- 

 nated in this way, for they are of such a nature as 

 to be of no use until highly developed. After they 

 get well enough developed to be used, it is easily 

 conceivable that they may be preserved by natural 

 selection, and even further perfected ; but at first 

 they are useless, and cannot therefore be selected. 

 This point can be made more intelligible by an 



