MORPHOGENESIS 795 



cell. Okada (1930) published fusion experiments on Actinosphaerium 

 and Arcella, which gave results comparable with those described by 

 Howland. 



The reincorporation phenomena in some of the Sarcodina appear to 

 offer a fertile field for studying the physical and chemical factors in- 

 volved in the union of cells or fragments. As yet the attention of very 

 few investigators employing Protozoa has been directed toward this end. 

 Miller (1932) studied cytoplasmic reappropriation in Arcella discoides 

 under the influence of different hydrogen-ion concentrations, as well as 

 under the influence of a low-voltage dc current. Within the limits of 

 pH 5.0 to pH 7.6, the rates of contact and fusion were not perceptibly 

 altered, although in media having a pH lower than 5.0 or greater than 

 7.6 the reappropriation reactions were retarded. Likewise the low-voltage 

 currents (0.3 to 2.1 microamps) failed to accelerate either contact or 

 fusion. Miller regarded reappropriation as wholly beyond the control of 

 pH or direct currents within the ranges tested. It occurred to Brehme 

 (1933) that the various Sarcodina in which reappropriation has been 

 reported are forms with relatively viscous protoplasm. She therefore 

 attempted fusion experiments with Amoeba proteus, a type with less 

 viscous protoplasm than those previously examined. Since A. proteus did 

 not reappropriate its own or foreign fragments, she was able to conclude 

 that increased viscosity may be an important factor in the fusion process. 



Richard Hertwig's (1903, 1908) karyoplasmic relationship hypothesis 

 has strongly influenced the more recent investigations of nuclear and 

 cytoplasmic phenomena. Taylor and Farber (1924) excised varying 

 quantities of the cytosome of Euplotes patella with a micropipette. Con- 

 trary to the results expected in accordance with Hertwig's rule, the 

 operated individuals continued to divide in the vigorous, normal fashion. 

 In Chaos diffiuens the initiation of division was believed by Phelps 

 (1926) to be a direct result of increasing the volume of cytoplasm, 

 whereas the removal of cytoplasm retards growth, and presumably divi- 

 sion, owing to the intervention of reconstruction processes. Similarly, 

 Causin (1931) maintained that the excision of fragments in Stentor 

 disturbs the K/P equilibrium and that this, in turn, initiates reorganiza- 

 tional activities which culminate in division or, more frequently, in 

 physiological regeneration. During periods of physiological regenera- 

 tion in 5". coeruleus, the number of macronuclear segments is regulated 



