A New Theory of Heredity. 81 



all that we know of the functions of the two sexual ele- 

 ments and if, besides fiirnishing an explanation of all the 

 phenomena which are accounted for by other hypotheses, 

 it embraces new classes of facts as well, the presumption 

 in its favor becomes still greater. 



Finally, if it leads to the discovery of new and un- 

 expected relations between phenomena, and to the estab- 

 lishment of laws which group and interpret phenomena 

 between which no connection had previously been re- 

 cognized, its value must be acknowledged. 



I venture, then, to advance a new theory of heredity, 

 which, briefly stated, is as follows: 

 \ The union of two sexual elements gives variability. 

 Conjugation is the primitive form of sexual reproduction. 

 Here the functions of the two elements are alike, and 

 the union of parts derived from the bodies of two parents 

 simply insures variability in the offspring. 



In all multicellular organisms the ovum and the male 

 cell have gradually become specialized in different direc- 

 tions. 



"!The ovum is a cell which has gradually acquired a 

 complicated organization, and which contains material 

 particles of some kind to correspond to each of the 

 hereditary characteristics of the species. 



The ovum, like other cells, is able to reproduce its 

 like, and it not ofriy gives rise during its development 

 to the divergent cells of the organism, but also to cells 

 like itself. 



The ovarian ova of the offspring are these latter cells, 

 or their direct unmodified descendants. 



Each cell of the body is, in a morphological sense, an 

 independent individual. It has the power to grow, to 

 give rise by division to similar cells, and to throw off 

 minute germs. During the evolution of the species it has 



