138 THE INDUCTIONS OF BIOLOGY. 



Any one adequately acquainted witli the facts, may readily 

 raise objections to this arrangement. He may name forms 

 which do not obviously come under any of these heads. He may 

 jX)int to plants that are for a time multicentral, but after- 

 wards develop axially. And from lower types of animals, he 

 may choose many in which the continuous and digcontinuous 

 modes are both displayed. But, as already hinted, an ar- 

 rangement free from such anomalies must be impossible, if the 

 various orders of organization have arisen by Evolution. The 

 one above sketched out, is to be regarded as only a rough 

 grouping of the facts, which helps us to a conception of them 

 in tlieir totality ; and so regarded, it will be of service when 

 we come to treat of Individuality and Reproduction. 



§ 51. From these most general external aspects of organic 

 development, let us now turn to its internal and more special 

 aspects. When treating of Evolution as a universal process 

 of things, a rude outline of the course of structural changes in 

 organisms was given {First Principles, §§ 43, 55, 56). Here, 

 however, it will be proper to describe these changes more fully. 



The bud of any common plant in its earliest stage, consists 

 of a small hemispherical or sub-conical projection. While 

 it increases most rapidly at the apex, this presently deve- 

 lops on one side of its base, a smaller projection of like general 

 shape with itself. Here is the rudiment of a leaf ; which pre- 

 sently spreads more or less round the base of the central 

 hemisphere or main axis. At the same time that the central 

 hemisphere rises higher, this lateral prominence, also in- 

 creasing, gives rise to subordinate prominences or lobes. 

 These are the rudiments of stipules, where the leaves are 

 stipulated. Meanwhile, towards the other side of the main 

 axis, and somewhat higher up, another lateral prominence 

 arising, marks the origin of a second leaf. By the time that 

 the first leaf has produced another pair of lobes, and the 

 second leaf has produced its primary pair, the central hemi- 

 sphere, still increasing at its apex, exhibits the rudiment of a 



