HEREDITY. 317 



where a lost limb or tail is replaced, but it is still more 

 remarkable in cases where, as among some annelids, the 

 pieces into which an individual is cut severally complete 

 themselves by developing heads and tails, or in cases like 

 that of the Ilolothuria, which having, when alarmed, ejected 

 its viscera, reproduces them. Such facts compel us to admit 

 that the components of an organism have a proclivity 

 towards a special structure — that the adult organism when 

 mutilated exhibits that same proclivity which is exhibited 

 by the young organism in the course of its normal develop- 

 ment. As before said, we may, for want of a better name, 

 figuratively call this power organic polarity: meaning by 

 this phrase nothing more than the observed tendency towards 

 a special arrangement. And such facts as those presented 

 by the fragments of a Hydra, and by fragments of leaves 

 from which complete plants are produced, oblige us to recog- 

 nize this proclivity as existing throughout the tissues in 

 general — nay, in the case of the Begonia phyllomaJiiaca, 

 obliges us to recognize this proclivity as existing in the 

 physiological units contained in each undifferentiated 

 cell. Quite in harmony with this conclusion, are 



certain implications since noticed, respecting the characters 

 of sperm-cells and germ-cells. We saw sundry reasons for 

 rejecting the supposition that these are highly-specialized 

 cells and for accepting the opposite supposition, that they 

 are cells differing from others rather in being unspecialized. 

 And here the assumption to which we seem driven by the 

 ensemble of the evidence, is, that sperm-cells and germ-cells 

 are essentially nothing more than vehicles in which are con- 

 tained small groups of the physiological units in a fit state 

 for obeying their proclivity towards the structural arrange- 

 ment of the species they belong to. 



If the likeness of offspring to parents is thus determined, 

 it becomes manifest, a priori, that besides the transmission of 

 generic and specific peculiarities, there will be a transmis- 

 sion of those individual peculiarities which, arising without 



