PRACTICAL STUDY OF THE CELL. 63 



the midrib of young fern leaves. Tote the abundant protoplasm, 

 large nuclei, central vacuole, and greatly thickened cell-walls. 



"We have now considered the general arrangement of living 

 matter in organisms, and some of its more important properties. 

 But it is impossible to derive adequate knowledge of vital struc- 

 tures and activities without prolonged and thorough study of 

 complete individual organisms which may be taken as more or 

 less typical of all. In this way only can we acquire complete, 

 connected and correct ideas of what living things are, how they 

 come into being, how they are constructed, how they live, and 

 how they are related to one another and to the lifeless world by 

 which they are surrounded. To this end a detailed account of a 

 common plant will now be given, followed by a similar analysis 

 of a common animal. If the biology of these organisms be really 

 mastered by studying the specimens, the descriptions and the 

 figures, the student will have been fairly introduced to many of 

 the most important principles of biology. 



