THE BEGINNINGS OF II FE. 543 



It must be recollected that difficulties always beset 

 our path when we attempt to define or separate by 

 hard and fast lines, things which — being evolved from 

 one another — are produced by a gradual process of modifi- 

 cation. It most frequently happens that no definition can 

 be framed which will not involve some contradictions. 

 All that remains, therefore, in such a case is to strive 

 to select that meaning for any word in question which 

 is most congruous with its usual meaning, and the 

 adoption of which will involve the fewest contra- 

 dictions. 



Without nov/ going into the reasons which have been 

 urged on both sides— and which have been very fairly 

 set forth by Dr. Carpenter^ — we will simply state that 

 we now agree with Mr. Herbert Spencer^ in thinking 

 the conditions above mentioned to be best fulfilled 

 by considering that ' a biological individual is any 

 concrete whole, having a structure which enables it, 

 when placed in appropriate conditions, to continually 

 adjust its internal relations to external relations, so 

 as to maintain the equilibrium of its functions.' 

 And then, as Mr. Spencer adds: — 'In pursuance of 

 this conception, we must consider as individuals, all 

 those wholly or partially independent organized masses 

 which arise by multicentral and multiaxial develop- 

 ment, that is either continuous or discontinuous. 

 We must accord the . title to each separate aphis, 



. 1 ' Principles of Comp. Physiol.,' 4th ed., 1854, pp. 523-529. 

 2 ' Principles of Biology,' vol, i. p. 207. 



