difference in faculty between the lowest plant and the 

 highest, or between plants and animals. But the differ- 

 ence between the powers of the lowest plant, or animal, 

 and those of the highest is one of degree, not of kind, 

 and depends, as Milne-Edwards long ago so well pointed 

 out, upon the extent to which the principle of the divis- 

 ion of labor is carried out in the living economy. In the 

 lowest organism all parts are competent to perform all 

 functions, and one and the same portion of protoplasm 

 may successively take on the function of feeding, mov- 

 ing, or reproducing apparatus. In the highest, on the 

 contrary, a great number of parts combine to perform 

 each function, each part doing its allotted share of the 

 work with great accuracy and efficiency, but being use- 

 less for any other purpose. On the other hand, notwith- 

 standing all the fundamental resemblances which exist 

 between the powers of the protoplasm in plants and in 

 animals, they present a striking difference (to which I 

 shall advert more at length presently,) in the fact that 

 plants can manufacture fresh protoplasm out of mineral 

 compounds, whereas animals are obliged to procure it 

 ready made, and hence, in the long run, depend upon 

 plants. Upon what condition this difference in the pow- 

 ers of the two great divisions of the world of life de- 

 pends, nothing is at present known. 



With such qualification as arises out of the last- 

 mentioned fact, it may be truly said that the acts of all 

 living things are fundamentally one. Is any such unity 

 predicable of their forms ? Let us seek in easily verified 

 facts for a reply to this question. If a drop of blood be 

 drawn by pricking one's finger, and viewed with proper 



