NUTRITION IN SENESCENCE AND REJUVENESCENCE 171 



whole animal of small size by development of a new posterior end 

 and a pharynx (Fig. 65), and is once more ready to feed and repeat 



Figs. 58-65. — Planaria velata: a life cycle without reproduction: Figs. 58-61, 

 the changes of advanced age; Figs. 62-65, ^^^ period of rejuvenescence. 



the life history. But in other cases the change in form continues 

 until nothing but the head remains active, as in Fig. 61, and then 



