[56 THE INDUCTIONS OF BIOLOGY. 



secretion and that to produce another ; each muscle as the 

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

 special ^ensation 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 general- 



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

 familiar and obvious one : the induction, namely, that com- 

 plexity of function, is the correlative of complexity of struc- 

 ture. The leading aspects of this truth must be briefly noted. 



Where there are no distinctions of structure, there are no 

 distinctions of function. One of the Rhizopods above 

 instanced as exhibiting life without organization, will serve 

 as an illustration. From the outside of this creature, 

 which has not even a limiting membrane, there are protruded 

 numerous thread-like processes. Originating from any point 

 of the surface, each of these may contract again and disap- 

 pear ; or it may touch some fragment of nutriment, which it 

 draws with it, when contracting, into the general mass thus 

 serving as hand and mouth ; or it mav 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 structureless 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 concomitant 

 fixed distribution of actions. Among plants we see that 

 when, instead of a uniform tissue like that of the Algce, 

 everywhere devoted to the same process of assimilation, 

 there arise, as in the Exogens, 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- 



