200 THE INDUCTIONS OF BIOLOGY. 



to propel blood; this gland as fitted to produce one requisite 

 secretion and that to produce another; each muscle as the 

 agent of a particular motion; each nerve as the vehicle of a 

 special sensation or a special motor impulse. 



It is clear that dealing with Biology only in its larger 

 aspects, specialities of function do not concern us; except in 

 so far as they serve to illustrate, or to qualify, its generalities. 



§ 57. The first induction to be here set down is a familiar 

 and obvious one; the induction, namely, that complexity of 

 function is the correlative of complexity of structure. The 

 leading aspects of this truth must be briefly noted. 



Where there are no distinctions of structure there are no 

 distinctions of function. A Rhizopod will serve as an illus- 

 tration. From the outside of this creature, which has not 

 even a limiting membrane, there are protruded numerous 

 processes. Originating fro^rn any point of the surface, each of 

 these may contract again and disappear, or it may touch 

 some fragment of nutriment which it draws with it, Avhen 

 contracting, into the general mass — thus serving as hand and 

 mouth; or it may come in contact with its fellow-processes 

 at a distance from the body and become confluent with them ; 

 or it may attach itself to an adjacent fixed object, and help 

 by its contraction to draw the body, into a new- position. In 

 brief, this speck of animated jelly is at once all stomach, all 

 skin, all mouth, all limb, and doubtless, too, all lung. In 



organisms having a fixed distribution of parts there is a con- 

 comitant fixed distribution of actions. Among plants we see 

 that when, instead of a uniform tissue like that of many 

 Algce, everywhere devoted to the same process of assimilation, 

 there arise, as in the higher plants, root and stem and leaves, 

 there arise correspondingly unlike processes. Still more con- 

 spicuously among animals do there result varieties of function 

 when the originally homogeneous mass is replaced by hetero- 

 geneous organs ; since, both singly and by their combinations, 

 modified parts generate modified changes. Up to the 



