156 Life as a Physical Ph n<<menon. 



amine when we have briefly considered how these units of 

 living structures are related and combined in higher 

 organisms. 



We have seen the life process in the most simple struc- 

 ture, let us trace its workings in more complex beings. 

 Cells do not always retain their spherical form, even when 

 they are originally BphereB. One of the first modifications 

 is an elongation in the direction of growth. 



Let us now advance one step in theprocess of existence. 



Here I represent a being, a plant consisting of several 

 such cells as have been described, and as we see, they are 

 elongated in the axis of growth. The cells are connected 

 at the extremities, and are thus united to make up a single 

 individual. Now the little green filaments which Ave have 

 all seen floating on the still waters, are, many of them, 

 made up just in this way — a single row of cells, con- 

 nected at the extremities. 



Let us examine another form. Here is a filament made 

 up of a single row of cells, but instead of being elongated 

 they are flattened. This is the appearance of certain sea- 

 weeds when placed under the lenses of the microscope. 



Now, let us take a very small thread of muscular fibre, 

 and place it in the field of the microscope. It will present 

 the'appearance of several of these little threads of sea-weed 

 placed side by side, and if we separate these lows of cells 

 and place a single ultimate fibre of muscle under the 

 glass, it may bo hard to tell which is the fibre of muscle 

 and which the thread of sea-weed. Thus we see that 

 a very large and important portion of the human body 

 is built on the identical plan of the structure of the hum- 

 ble weed. And do we not see also how rapidly we have 

 advanced in the scale of being? We commenced with the 

 Bimplesl living Btructure, the slime in the pool, then we 

 examined a being scarcely higher in the scale of life, and 

 theu by the most natural and easy advance came directly 



