WASTE AND REPAIR. 225 



to these units which possess the property of arranging them- 

 selves into the special structures of the organisms to which 

 they belong; it will be well here to ask by what name they 

 may be most fitly called. 



On the one hand, it cannot be in those chemical com- 

 pounds characterizing organic bodies that this specific pro- 

 perty dwells. It cannot be that the molecules of albumin, 

 or fibrin, or gelatine, or other proteid, possess this power of 

 aggregating into these specific shapes; for in such case there 

 would be nothing to account for the unlikenesses of different 

 organisms. If the proclivities of proteid molecules deter- 

 mined the forms of the organisms built up of them or by 

 them, the occurrence of such endlessly varied forms would 

 be inexplicable. Hence what we may call the chemical units 

 are clearly not the possessors of this property. 



On the other hand, this property cannot reside in what 

 may be roughly distinguished as the morphological units. The 

 germ of every organism is a minute portion of encased pro- 

 toplasm commonly called a cell. It is by multiplication of 

 cells that all the early developmental changes are effected. 

 The various tissues which successively arise in the unfolding 

 organism, are primarily cellular; and in many of them the 

 formation of cells continues to be, throughout life, the process 

 by which repair is carried on. But though cells are so 

 generally the ultimate visible components of organisms, that 

 they may with some show of reason be called the morpholo- 

 gical units; yet we cannot say that this tendency to aggre- 

 gate into special forms dwells in them. In many cases a 

 fibrous tissue arises out of a nucleated blastema, without 

 cell-formation; and in such cases cells cannot be regarded as 

 units possessing the structural proclivity. But the conclusive 

 proof that the morphological units are not the building 

 factors in an organism composed of them, is yielded by their 

 independent homologues the so-called unicellular organisms. 

 For each of these displays the power to assume its specific 

 structure. Clearly, if the ability of a multicellular organism 



