RELATION BETWEEN AMITOSIS AND MITOSIS. 1 69 



Cuticle-forming cells of the external layer of the body are 

 shown in Figs. 17-19. These cases are taken from the region 

 where proglottids are beginning to form : in this region division 

 is more frequent in these cells than in proglottids advanced in 

 development. 



It is perhaps unnecessary to repeat that these figures are 

 merely a few cases selected almost at random from among my 

 camera-drawings. The number of figures might be increased 

 almost indefinitely if desirable, but I think these are sufficient to 

 show that amitosis is a typical feature of development in Moniezia 

 both in the germ cells and in the soma. 



Unfortunately it is at present impossible to complete my obser- 

 vations by examination of the stages between the embryo and 

 the adult tape-worm, for the life-history and intermediate host 

 of the genus are unknown. 



V. General Discussion and Conclusions Concerning Ami- 

 tosis and Mitosis in Moniezia. 



Before any general interpretation of the facts concerning the 

 role and frequency of the two forms of division is possible it is 

 necessary to know something regarding the physiological condi- 

 tions which determine the occurrence of each of the two methods 

 of division. At present, however, we have no real knowledge 

 regarding these conditions and are limited to hypotheses and sur- 

 mises. In a recent paper (Child, 'oyc) I have made certain sug- 

 gestions along this line to which attention may be called here. 



It was pointed out in the paper referred to that the stimulus to 

 nuclear division and growth is apparently not identical with the 

 presence of an excess of nutritive material, for it is a well known 

 fact that extensive regeneration will occur in many forms, e. g., 

 Planaria, even after reduction of the body by long continued 

 starvation, to a fraction of the original size. In such cases the 

 regenerating region derives its nutritive material from other 

 regions of the body, which consequently decrease in size more 

 rapidly than in individuals where no regeneration is taking place. 

 Evidently in such cases the nutritive material goes to the regen- 

 erating region at the expense of other parts because the demand 

 is greater there than elsewhere. In short, conditions exist in this 



