76 THE DATA OF BIOLOGY. 



stance in the environment capable of transformation into its 

 own tissue ; but that the introduction of these masses into its 

 stomach, shall be followed by the secretion of a solvent fluid 

 that will reduce them to a fit state for absorption. Special 

 outer properties must be met by special inner properties. 



When, from the process by which food is digested, we 

 turn to the processes by which it is seized, we perceive the 

 same general truth. The stinging and contractile power of 

 a polype s tentacle, correspond to the sensitiveness and 

 strength of the creatures serving it for prey. Unless that 

 external change which brings one of these creatures in con 

 tact with the tentacle, were quickly followed by those inter 

 nal changes which result in the coiling and drawing up of 

 the tentacle, the polype w r ould die of inanition. The funda 

 mental processes of integration and disintegration within it, 

 would get out of correspondence with the agencies and pro 

 cesses without it ; and the life would cease. 



Similarly, it may be shown that when the creature be 

 comes so large that its tissue cannot be efficiently supplied 

 with nutriment by mere absorption through its limiting 

 membranes, or duly oxygenated by contact with the fluid 

 that bathes its surface, there arises a necessity for a circu 

 latory system by which nutriment and oxygen may be dis 

 tributed throughout the mass ; and the functions of this sys 

 tem, being subsidiary to the two primary functions, form 

 links in the correspondence between internal and external 

 actions. The like is obviously true of all those subordinate 

 functions, secretory and excretory, that facilitate oxidation 

 and assimilation functions in which we may trace, both co- 

 temporaneous changes answering to co-existences in the en 

 vironment, and successive changes answering to those changes 

 of composition, of temperature, of light, of moisture, of pres 

 sure, which the environment undergoes. 



Ascending from the visceral actions to the muscular and 

 nervous actions, we find the correspondence displayed in a 

 manner still more obvious. Every act of locomotion implies 



