(3) 



Inheritance in the Asexual Reproduction of 

 Centropyxis aculeata. 



Introduction . 



The "Pure Line" Concept. Since Johannsen (1903). 

 as a result of his studies on self-fertilized plants, first 

 enunciated the concept of "pure lines", the phenomenon to 

 which he gave thiis name has been shown, by a multitude of 

 other investigators, to be of very general occurrence. It 

 has been proved that the same general state of affairs 

 exists, not only in self-fertilized plants, but also in 

 plants reproducing vegetativoly , by tubers or cuttings, and 

 in animals reproducing by parthenogenesis, budding, and 

 fission. It is unnecessary to enter into the details of 

 these investigations. I y/ill only mention the papers of 

 East (1910) Oh. the potato, of Agar (1914) and Ev/ing (1914, 

 1914a, 1916) on daphnids and aphids reproducing partheno- 

 genetically, of Kanel (1908) and Lashley (1915, 1916) on 

 Hydra, and of Barber (1907), Jennings (1908) and .iinslow 

 and ;Valker (1909) on protozoans and bacteria. All these 

 investigators entirely corroborated the results and con- 

 clusions of Johannsen. 



And what are these conclusions? Simply that in organ- 

 isms reproducing asexually and in homozygous organisms 

 reproducing by self-fertilization, each species is not an 

 ultimate unit, but is itself made up of a largo number of 



