Heredity in Protozoa 585 



would be carried right on from generation to generation, and hence 

 structural foundations for a whole animal world such as we now 

 see could be laid in a relatively short period as compared with the 

 time necessary to advance organization in forms limited to repro- 

 duction by germs. In fact the fundamentals could all be estab- 

 lished within the realm of the unicellular Protozoa" (p. 307). 



In my book on the Behavior of Lower Organisms, I expressed 

 similar ideas, with particular reference to the inheritance of ways 

 of behaving: 



"In the unicellular organisms there seems to be nothing in the 

 way of this inheritance by the offspring of the reaction-methods 

 acquired by the parent. There is no distinction between the germ 

 cells and body cells in these organisms: all acquirements pertain 

 to the reproductive cells. Through reproduction by division the 

 offspring are the parents, merely subdivided, and there is no evi- 

 dent reason why they should not retain the characteristics of the 

 parents, however these characteristics were attained. If this is 

 the real state of the case, then in unicellular organisms the life of 

 the race is a direct continuation of the life of the individuals, and 

 any acquirements made by the individuals are preserved to the 

 race" (Jennings '06, p. 320). 



Now, if this difference between unicellular and multicellular 

 organisms actually exists, it is evidently of the highest interest 

 and importance. Yet there have been no investigations of the 

 matter to see if there really is such a difference. Our first task 

 is then to examine the phenomena from this standpoint; attempt- 

 ing to determine whether characteristics acquired during the 

 lifetime of the individual* are inherited by the progeny. At the 

 same time, we shall keep in mind the broader aspects of our prob- 

 lem, endeavoring to work out in general the relation of reproduc- 

 tion in the Protozoa to heredity. 



*I use for convenience the term "'individual," as commonly employed, to signify in the Protozoa 

 the separate free cells. I have no wish thereby to take any stand on Calkins' contention that the entire 

 cycle of cells derived from a conjugating pair corresponds to the individual of the Metazoan (Calkins 

 '06). The present paper deals with certain existing phenomena, which are not altered by the views 

 one may hold on this point. The relation of conjugation to heredity is to be taken up in a later 

 communication. 



