INTERiNAL CAUSES OF VARIATION 171 



afterward ; but what about their character ? In what condition 

 have they emerged from this seemingly incomprehensible tangle ? 

 Is nature as careful to preserve their quality as it is their number ? 



What opportunities for profound variation ! Certainly if 

 chromatin matter has any fundamental meaning, and if chromo- 

 somes are in any way representative of physiological units, 

 and if they in their turn are in any way representative of racial 

 characters, these processes must have some meaning in varia- 

 tion. Certainly we have been very near in all this to the material 

 basis of transmission of racial characters, and to fundamental and 

 initial causes of variation. 



Something has been lost in the two peculiar divisions attend- 

 ing maturation. Some definite groupings of hereditary substance 

 have disappeared from the line of descent. They could not have 

 represented, ordinarily, definite portions of a body, but they must 

 represent something. What chances for accident ! And, in the 

 light of these marvelous phenomena, do we wonder that individ- 

 uals are sometimes born minus a leg, an arm, or some other part ? 

 Do we wonder that vital parts are so often affected, and that one 

 third of our children die in infancy ? How many die before birth, 

 and how many more die at some stage in embryo ! 



Evidently all that is required to make a living being is a 

 fairly perfect development of the vital parts, quite regardless of 

 the presence or absence of the many other racial characters 

 that should be present in the perfect individual. Is it surprising 

 that perfect individuals are so few, and that defectives are 

 frequently so far from the type ? Here is material for study 

 on the part of criminologists and courts of justice, as well as 

 students of methods of economic improvement. 



Reduction and fertilization in plants. It may be said in 

 general that in animals the evidence tends to the assumption 

 that reduction takes place at the extrusion of the second polar 

 body ; that each group (rod, ring, or V-shaped body) is in reality 

 a doubled (bivalent) chromosome, and that the first polar body 

 removes one half of each (split) chromosome, while the next 

 removes every alternate chromosome. 



While the facts of reduction in plants are not yet fully worked 

 out, it is safe to say that the evidence tends to show that no 



