776 



MORPHOGENESIS 



division, the tendency to regenerate was slightly greater than before. 

 These fragments sometimes regenerated in the absence of micronuclear 

 material. The highest percentage of successful regenerates was obtained 

 as the cells entered upon the division period. When Uronychia was cut 

 in the early prophase, either transversely or obliquely in a region anterior 

 to the presumptive division plane, three complete individuals were pro- 

 duced (Fig. 179). Three individuals instead of two resulted in such 

 cases, because the predetermined division plane was not appreciably 



Figure 179. Regeneration in Uronychia transfuga. A, transection made anterior to the 

 division plane in mid-division phase (B, C, and D show the results after twenty-four 

 hours) ; B, small amicronucleate individual derived from the anterior fragment; C and D, 

 anterior and posterior daughters produced when the large posterior fragment divided. 

 (From Calkins, 1911a.) 



altered by the type of cut just described. The small amicronucleate an- 

 terior piece regenerated a diminutive organism whose morphological 

 features were normal. Fission occurred in the large posterior fragment 

 soon after the healing of the cut surface. A small anterior regenerated 

 daughter and a normal posterior daughter were the products, both of 

 which were normal as regards nuclear apparatus. The regenerative power 

 diminished in the mid-division phases, inasmuch as one or another of 

 the three cells frequently failed to regulate. As the division process 

 drew to a close, reparative regeneration reached its lowest ebb; those 

 which did regenerate were low in vitality and short-lived. In regard to 



