788 MORPHOGENESIS 



of regeneration is one which includes restoration of function as well as of 

 structure [p. 250]. 



Notwithstanding the evident truth that maintenance and perpetuation 

 are ends to which all of the vital functions are directed, our criteria of 

 recovery need not be so inclusive, if the practical objectives of the ex- 

 perimental laboratory are to be realized. To those interested in the 

 mechanisms of form determination, the ultimate fate of a regenerate is 

 of secondary importance. Pieces from starved Protozoa do not grow, but 

 they are frequently capable of regenerating new individuals of propor- 

 tionate size. Amicronucleate fragments of some ciliates are sometimes 

 capable of regenerating without being able to maintain the redifferenti- 

 ated state or to divide. The success of regenerative processes in such 

 instances is limited only to the extent to which they are correlated with 

 the general maintenance functions. 



According to Stole (1910), cytoplasmic bits of Amoeba may live for 

 as much as thirty days and are able to prehend, ingest, digest, and as- 

 similate food. In agreement with Verworn, Lynch (1919) found evi- 

 dences of all the usual catabolic activities, but his enucleated amoebulae 

 showed no symptoms of growth, regeneration, or division. A few years 

 later, Phelps (1926) concluded that merozoa from Amoeba do not 

 carry on any of the fundamental body processes except locomotion. 

 Nevertheless, she did note an increase in the number of crystals within 

 the fragments which, according to her own criteria, denotes metabolic 

 change. Others have reported only dissociated movements in cytoplasmic 

 fragments of Amoeba (Willis, 1916; Mast and Root, 1916). Quite a 

 number of merotomists have recorded instances of fusion between enucle- 

 ated bits of cytoplasm with the parent cell in various Foraminifera, 

 Heliozoa, and testate rhizopods (see p. 793). In Actinophrys sol the 

 fragments fuse with one another (Looper, 1928). 



The survival of enucleated ciliate fragments, even for short periods, 

 is not the general rule. There appear to be only few instances recorded 

 in the literature in which such fragments show any tendency to re- 

 differentiate. Gruber (1886) reported that redifferentiation occurs in 

 enucleated fragments derived from dividing stentors, provided a de- 

 veloping peristome is included in each piece. Cytoplasmic portions of 

 Blepharisma are sometimes capable of form regeneration, but since they 

 are unable to feed involution and cystolysis soon occur (Moore, 1924). 



