A CRITICAL EXAMINATION 39 



the other parent. Studies of this sort are bound 

 to throw hght on the puzzling — and too much 

 neglected — problem of dominance. 



III. Conclusion 



In what has preceded we have attempted a 

 critical analysis of the four general methods which 

 have been employed in the investigation of the 

 problem of heredity. Two of these methods have 

 been seen to be essentially statistical, and two 

 essentially biological. The statistical methods — 

 the biometric and the Mendelian — differ funda- 

 mentally only in that the former investigates 

 primarily the ancestry and the latter primarily the 

 progeny. Logically exactly the same distinction 

 was found between the two purely biological 

 methods — the cytological and the embryologi- 

 cal. The former studies the ancestry of the germ 

 cell (gametogenesis) , the latter the progeny of 

 the germ cell (somatogenesis). 



All of these methods are valuable, and each 

 has contributed to our present knowledge of 

 heredity. No one of the methods alone can, 

 however, solve the problem. They all have at 

 least one fundamental limitation in common. 

 This is that they offer no means of directly getting 

 at any definite information regarding the origin, 

 cause, or real nature of that specificity of living 

 material which is the very foundation of the phe- 



