THE PROTOPLAST 



Fio. 21. PROTOPLASM. 



A speck of the simplest form of living 

 Much magnified. 



life ; a microscopic water-plant often to be 

 met with in rain-water cisterns, or as green 

 and reddish incrustations in damp places. 

 Sphcerella (fig. 24) is a plant of a single 

 cell ; and as we desire to speak a little of 

 the life-history of a single cell, it may be 

 well to take a nearer view of this tiny 

 organism. 



If you take some rain-water from a 

 cistern into which the sun has been shining 

 for a few hours, and examine a drop of it 

 under the microscope, }'ou will probably 

 find that it is teeming with life. Minute 

 pear-shaped bodies of a green colour swim 

 rapidly about (fig. 24), propelling them- 

 selves along by delicate filaments of a 



transparent substance, which branch out, two on each individual, from 

 a tiny red spot (termed the eye~spot), which might at first be thought to 

 be a head. The movement is due to the alternate shortening and lengthen- 

 ing of these filaments or flagella, which are so fine and transparent, and 

 lash the water so rapidly as to be scarcely visible. By-and-by the move- 

 ment becomes slower, and ceases ; the flagella disappear ; the green 

 bodies, as though ashamed of swimming about in their nakedness so long, 

 form little jackets for themselves of a substance hereafter to be described, 

 and sink to the bottom of the water, where they enter upon a new stage 

 of existence. 



The active, motile stage is at an end ; the giddy childhood time is 

 passed ; an autumnal red has blended 

 with the fresh green hue of youth (for 

 the spent swimmers have partially changed 

 their colour) ; and the adult or stationary 

 stage has commenced. You continue to 

 watch one of these quiescent bodies. It 

 has lost its pear shape now, and has 

 grown larger. Presently a process of 

 rearrangement is seen to be going on 

 inside the little membranous sack. 



The contents divide into two portions, 

 each of which again divides : and with 

 that there is a fresh formation of pro- 

 tective membrane, for each of the four 

 bodies must have its own cellulose in- 

 vestment, and note this well ! each 

 weaves its own. And now we have no 

 3 



FIG. 22. AMCEBA. 



A. One of the simplest forms of animal life. B. The 



same capturing an Actinophrys. Magnified about 



80 times. 



