2-8 



PROTOPLASM AND THE CELL. 



direction of the flow. If particles of food be met with, the 

 protoplasm flows around them, and when they have been digested 

 within the body, the protoplasm flows onward, leaving the refuse 

 behind. Hour after hour and day after day this flowing may 

 go on, and there is perhaps no 

 more fascinating and suggestive 

 spectacle known to the biologist. 

 A similar change of form is ex- 

 hibited by the colorless corpuscles 

 of amphibian and other blood, in 

 which it may be observed, though 

 far less satisfactorily, if Amasbce 

 cannot be obtained. Among plants, 

 protoplasmic movements of perhaps 

 equal beauty may be observed. 

 One of the simplest is known as the 

 rotation of protoplasm, which may 



f^SS! 



''''' t-~'-'\\ 



M^b&Sj 



: %t:_ 



*: : )-V.; : ' 6 ,.":": f" *- 



ili^liSi 



J -,--. .- i- -- 



^ : ^ISSS' 



-V. 



.n, 



FIG. 17. A cell of a stonewort (Nitel- 

 la) showing the rotation of proto- 

 plasm ; the arrows show the direc- 

 tion of the flow, m, membrane of 

 the cell; w, nucleus, opposite to 

 which is a second ; p, protoplasm ; v, 

 large central vacuole filled with sap. 



^jfP^H^^^Ml 



HV^^S^^I:!^!! 



KSi^l ISW 

 fc;^ irft^BSr 



,,;-%?)o^ : :' ^; < ?'i s '-ov 

 ^V-^a-iH-s.p.'^ft^isi^? 



c~':v v.^r^: -.^n^- 

 /U^ ;: '!4MlH!ciS 



j:: ,v;:o P; b-^i-i'.tfc.ni^ 

 ; i ...:-- t ?-'. ; 6- : "' l v^ ; ^^ 



|l|^^p?|Sf| 



n 



FIG. 17tt. Two cells and a part of a 

 third from the tip of a "leaf" of a 

 stonewort, showing rotation of the 

 protoplasm in the direction of the 

 arrows. 



be studied to advantage in rather young cells of stoneworts (Char a 

 or NitellcC). These cells have the form of short or elongated 

 cylinders which are often pointed at one end (Fig. 17). The 



