Protoplasm, the living stuflf of organisms, is a very complex mixture of 

 many different substances. It is distributed in more or less distinct and 

 specialized units called cells. 



In all kinds of organisms the protoplasm of each cell grows, reproduces, 

 moves, antl is irritable. In the larger plants and animals individual cells 

 carry on specialized activities in addition to the fundamental ones. 



EXPLORATIONS AND PROJECTS 



1 To survey the "whole plant", compare in several difTercnt kinds of plants 

 the main structural parts; look for and record suggestions as to the different ways 

 in which each part contributes to the life of the plant. 



2 Study grasshoppers. Note and list the many things that this living organ- 

 ism does but that nonliving objects do not do. Note carefully also how it does 

 everything it does. Watch for breathing movements. 



3 To find out in what ways a living frog differs from nonliving matter, 

 tabulate observations on a living frog and corresponding characteristics and activi- 

 ties of a nonliving object. Attend especially to indications of sensitiveness. Look 

 for indications of breathing and for the manner of breathing; for differences in 

 behavior in the water and in the air; for the use of feet in swimming, in jumping; 

 for ways of getting and eating food. 



4 To observe cells, tear a bit of the thin skin from an inner layer of an 

 onion, place it on a microscope slide in a drop of water, lay a cover slip over it, 

 and examine under the low power of the microscope. To stain the tissue, touch a 

 drop of ink to the edge of the cover slip. 



By a similar procedure observe other plant cells — for example, a bit of the 

 underskin of a leaf; some pond scum; some green-slime scraped from a piece of 

 wet bark; some yeast cells from a crushed bit of yeast cake; small leaves from peat 

 moss and from elodea or other water plants; the skin of a potato; or the skin of 

 a flower petal. In most cases it will be possible to make out the cell walls, the 

 nucleus, and greenish bodies called chloroplasts. 



Examine groups of cells from various animal sources. Take scrapings from the 

 inside of your own mouth or that of a frog, or other animal. 



Examine a culture of Ameba proteus or of Chaos chaos. Note the forms, num- 

 bers, and movements of the pseudopods. What seems to be going on just inside of 

 the forward-moving tip? Look for changes in direction of movements; for the 

 engulfing of food material. Compare the form and structure of the ameba with 

 other cells that you have studied. 



27 



