256 LEISURE-TIME STUDIES. 



many investigators, held that all the tissues and membranes 

 of the bodies of animals and plants originated from minute 

 rounded structures named "cells" (Fig. 39), which were 

 readily demonstrated by microscopic investigation to occur 

 in every part of living tissues. When animals and plants 

 grow they may indeed be said to grow through the increase 

 of their constituent parts the cells, and these latter are re- 

 garded by modem physiologists as representing not merely 

 the actual units of the living body, but as containing in them- 

 selves the powers and qualities which characterise the being 

 of which they form part. Nor does the cell-theory of 

 organisation rest with the assertion that the animal or plant- 

 body is a collection of cells. The germ of the plant or 

 animal, through the development of which the most compli- 

 cated body is in time produced, can be shown to be repre- 

 sented by a simple cell, endowed with powers of special and 

 characteristic kind. Nay, more, it is equally true that the 

 lowest animals and plants appear before us as simple cells, 

 living a separate and disconnected 

 existence, and endowed with the 

 power of representing in their lives 

 the concentration of the actions which 

 the aggregated cells of higher beings 

 . 4 o.- Yeast-plants, each collectively exhibit. A red-snow-plant, 

 :elh or any of the lowest plants or alga, or 

 a yeast-plant (Fig. 40), exhibits all the characters of a simple 

 isolated cell, which in the latter case may be seen to grow, 

 to nourish itself, and to reproduce its like in the most perfect 

 manner, and to cause by its mere act of living the curious 

 series of phenomena to which the term " fermentation " has 

 been applied. 



Structurally regarded, then, by aid of the microscope, 

 animal and plant bodies are seen to present a most singular 

 identity of composition, in respect of the fact that both 

 bodies are primatively cellular, and that the lowest members 

 of each group exist as simple isolated cells. But the facts 

 revealed in 1837-38 merely formed the introduction to new 



