164 The Descent of Man. 



cuvc-iueu tilt' cliiu is ;iliuust wanting. A recent discovery 

 of lumuin remains of the pre-Indian period in Arizona, goes 

 to show that primitive man was deficient in speech, as these 

 skeh'tons retain the primitive distinction of other speech- 

 h'ss mammalia, in having the hyoid bones separated. In 

 man as we now know him, these bones are consolidated, 

 forming a single bone. 



The general theory of descent rests npon the study of 

 species in detail. Tliere can be no doubt in the mind of 

 the student that the specilic lines of definition are movable. 

 Each species has stages of variability, when it is com- 

 paratively plastic, and susceptible of change, before it 

 has developed an unyielding contour and form. After- 

 wards they develop into fixed types, and do not evolve 

 into other species thereafter. This is the condition in 

 which we hud most of the animal forms at the present 

 day. Our cats, for example, are not variable, or are 

 variable only within specilic limits. Dogs, on the contrary, 

 are very variable, and so are barn-yard foAvls. Mankind is 

 in a condition of plasticity or variability, and herein lies 

 great promise of human progress in the future. 



In attempting to account for the evolution of man, we 

 have two theories, one of Lamarck and the other of Darwin. 

 Lamarck devoted himself to explaining the origin of 

 species, but not to the special problem of natural selection. 

 The post-Darwdnians, as they have been happily named by 

 Eomanes, have generally accepted Darwin's hypothesis as 

 a complete explanation of evolution, but we are beginning 

 to see that Lamarck's views cannot be set aside, and that it 

 is of great importance in explaining the orir/m of variations. 

 Without it, natural selection would have no opportunity for 

 operation. The Darwinians say that animals and plants 

 have a tendency to variation. But nothing happens acci- 

 dentally — there can be no variation without a cause. Seek- 

 ing ovit these causes of variation is the province of a certain 

 school of biologists at the present time. To this study, the 

 great nations of the Avorld are all contributing. Chemistry 

 has been called a French science. In embryology Germany 

 stands at the head. Palaeontology will doubtless constitute 

 the contribution of America to this investigation. A rich 

 field for this investigation exists in our Western States and 

 territories, rivalled only by a similar field in the' Argentine 

 Eepublic. The fact that the earth cooled first at the poles, 



