24 INTRODUCTION TO NATURAL HISTORY. 



suitably to their wants. Thus the female insect shall either stimulate 

 a leaf, when it lays its eggs on it, or the eggs or the young when 

 hatched shall stimulate the leaf to such action as shall oblige it to en- 

 close the egg or maggot, and to prepare its future nourishment while 

 in the maggot state. For instance, the insect while in the maggot 

 state shall live on the leaf of a tree, using it as food ; and, when it 

 goes into its chrysalis state, it shall stimulate the leaf, which stimulus 

 shall make it roll up and enclose the insect. 



Of Motion in Vegetables. 



As vegetables have not progressive motion, it must necessarily 

 happen, that, whatever motion they have must be only a change of 

 position of some of the smaller [and moveable] parts upon the larger 

 and fixed ; making the larger parts always the fixed. This change in 

 the position of their smaller parts I believe arises in general from two 

 causes, viz. stimuli or influence, and internal irritation. 



To understand more thoroughly the motion in vegetables, we are to 

 consider the vegetable itself, in most instances, as consisting of three 

 parts : one, an old almost completely formed part ; the second, a new 

 forming part, viz. the new circle of wood and the new shoot; the third, 

 a temporary part, as the leaf, flowers, &c, which only serve a present 

 purpose, carrying on the operations of the plant when in its active life. 



The first very probably has no motion with respect to space ; the 

 second very probably is the cause of the whole bending in consequence 

 of external influence, as when a tree bends towards the light, or a 

 tree on the edge of a thicket bends towards the open air and recedes 

 from the thicket. As to the third or temporary parts; the leaves 

 are, most probably, necessary for the growth of the new circle of wood 

 and the new shoot ; and the flowers for the seed. It is in this third 

 [class of parts] that we are to expect the greatest quantity of motion : 

 the already formed parts appear to be almost stationary, with respect 

 to growth, in themselves or to that of other parts. 



On the Study of Natural History. 



In Natural History we are often made acquainted with the facts, yet 

 do not know the cause. Therefore we are obliged to have recourse to 

 experiment to ascertain the causes which connect the facts, one leading 

 into the other, making a perfect whole ; for, without the knowledge of 

 the causes and effects conjointly, our knowledge is imperfect. 



Writers on the jSTatural History of animals have been of two kinds 

 — one [concerned in] only what they could observe externally, such as 

 form and mode of life ; the second [studying only] the internal parts 



