6 4 GENERAL BIOLOGY 



The protoplasm may be removed from an internodal cell 

 by snipping off one end of it with scissors (after it has been 

 wiped dry) and squeezing the contents out upon a slide. 

 The largest available cells should be selected, for even then 

 the drop of protoplasm obtained is a minute one. Still it is 

 large enough to see and to handle. One may lift it on the 

 point of a needle, and test its viscosity. One may see it 

 with the microscope, wholly uncovered. And if, in looking 

 at it, there is little to be seen, there is enough to reflect upon 

 in the fact that this inert and apparently well-nigh structure- 

 less mass is the essential living part of every living thing, 

 much the same in all, and, despite appearances, the builder 

 of all the array of organic life. It is this substance that in 

 the long aeons of the past has reclaimed the earth, and 

 clothed it with verdure and peopled it. 



The record of the foregoing study may well consist in 

 drawings of some of the things seen, such as: 



A few filaments of Spirogyra, showing their common 

 features and the individual differences between them. 



A single Spirogyra cell showing all the parts in detail. 



A bit of the chlorophyl band, highly magnified, show- 

 ing its form, the median ridge upon it, the py- 

 renoids, and starch granules. 



A cell treated with dilute glycerine, showing the shrunken 

 protoplasmic capsule withdrawn from the cell wall. 



A diagram of the internodal cell of Nitella, showing 

 the direction of the protoplasmic current. 



THE FORM OF THE PLANT BODY IN COMMON ALGAE. 



Some hints of the diversity of form in algae will have 

 been gained from the study of Closterium, Spirogyra and 

 Nitella the first, unicellular; the second, a linear aggre- 

 gate, its cells all alike; and the third, a branching, well-in- 

 tegrated body of cells of very different sizes, with terminal 

 buds and apical growth. 





