THE STRUCTURAL BASIS OF THE BODY 



29 



Their movements continued for "a short time and then ceased, though the 

 pulsations of the contractile vesicle were but little affected. The power 

 of digestion of food was completely lost. Other observers have shown 

 that Stentor, an infusorium which possesses a fragmented nucleus, may be 

 broken up into fragments of all sizes. Nucleated fragments as small as 

 one-twenty-seventh the volume of the entire animal are still capable of 



a 





FIG. 9. Regeneration in the unicellular animal Stentor. (From GRUBEK after BALBIANI.) 

 A. Animal divided into three pieces, each containing a fragment of the nucleus. 

 B. The three fragments shortly afterwards. C. The three fragments after twenty-four 

 hours, each regenerated to a perfect animal. 



regeneration. The wound quickly heals and the special organs the mouth, 

 with its surrounding cilia, and the contractile vacuole are regenerated, but 

 all non-nucleated fragments quickly perish (Fig. 9). 



Many similar observations have shown that the non-nucleated cytoplasm, 

 though it may survive for some time and perform normal movements in 

 ponse to stimuli, such as those of ingestion of food particles, loses entirely 

 e power of digestion, secretion, and growth. In animals possessing a shell, 

 a small secretion of the lime salts may occur on the surface, but this process 

 apidly comes to an end as the store of material in the cytoplasm is exhausted, 

 vegetable cells it is possible to break up the protoplasm by means of 

 lasmolysis into nucleated and non-nucleated parts. The nucleated part 

 uickly forms a new cell wall. The non-nucleated part is unable to effect 

 is formation, and soon dies unless it is in connection with an adjacent 

 11 containing a nucleus by means of fine threads of protoplasm which 

 s through pores in the intercellular septa (Fig. 10). In the higher animals 



res 

 the 



