MORPHOGENESIS 793 



the nuclear mass of the amicronucleate race as an undifferentiated prod- 

 uct of the amphinucleus. 



Behavior of Fragments: Grafting and Reincorporation 



Balbiani (1888) and Verworn (1889) were first to remark that parts 

 of ciliates move in the general manner of the entire animals. In his 

 work on Stylonychia, Oxytricha, and Paramecium, Jennings (1901) 

 emphasized body shape and the activity of heavy oral cilia as determining 

 factors in the characteristic swimming movements, whereas Ludwig 

 (1929) ascribed the spiral progression of ciliates to a more vigorous 

 activity of the aboral rather than the oral cilia. Bullington (1925) and 

 Horton (1935) discovered that the spiral movements do not neces- 

 sarily relate to the configuration of the oral groove. It appears that por- 

 tions of Infusoria in which oral cilia are lacking react in a fashion much 

 the same as that of the whole organisms; and, further, that the spiral 

 motions are not entirely dependent upon body shape or the activity of 

 oral cilia, but are produced by the coordinated activity of the body cilia 

 in general (Horton). 



The responsiveness of ciliate fragments to mechanical and chemical 

 stimuli was investigated in some detail by Jennings and Jamieson 

 (1902) . They found that if the fragments were not too small or irregu- 

 lar in form, the motor and sensory capacities compared favorably with 

 those of the intact individuals. On the contrary, Alverdes (1922) re- 

 ported some degree of sensory localization, wherein only the anterior 

 halves of 'Paramecium and Stentor were responsive to chemical stimula- 

 tion. More recently, Horton (1935) ascertained the sensitivity of the 

 anterior and posterior halves of P. caudatum to weak acid stimulation. 

 The results are in general agreement with the earlier work of Jennings 

 (1901). Unlike his predecessors, Horton noted that the posterior halves 

 of this species are somewhat more sensitive to weak acid stimuli than 

 are the anterior halves. 



The anastomosis of protoplasmic streamers in myxopods and the re- 

 combination phenomena in Foraminifera (Verworn, 1892; Jensen, 

 1896) was known to pioneer students of the Protozoa. In recent years 

 numerous other workers have discovered that excised, anucleate frag- 

 ments of many types of Sarcodina will recombine with the parental cell 



