BEHAVIOR OF ISOLATED CELLS 217 



4. Thin refractive surface membrane, the plasmalemma, which forms irregular 

 surface bulges. This is semi-solid. Movements are initiated and executed by 

 forces localized in this layer or membrane but "they may be associated with 

 local solation and re -gelation of that portion of the endoplasm which underlies a 

 fully developed ectoplasmic bulge. " (Holtfreter) 



The adhesiveness of isolated embryonic cells is associated with the fluid environment, 

 the developmental stage of the cells, and the cytological type of cell involved. Cells in 

 isolation tend to lose their adhesiveness, and the hyaline bulges of the moving cells are 

 less adhesive. Adhesion is definitely toward other cells rather than toward the substra- 

 tum such as glass. Cytolizing cells become non-adhesive and are generally expelled 

 from an aggregation of cells. 



Any living cell which exhibits amoeboid movement, forming lobopodia, would be expected 

 to phagocytize particles from the environment. Some of these embryonic cells are more 

 efficient than others, the difference being the more apparent in cells from the neurula 

 stage. 



Holtfreter has been able to keep isolated embryonic cells of the Amphibia alive and active 

 'for weeks. There is around each cell an elastic surface coat whose strength increases 

 during development (differentiation) and whose existence is important in the behavior, 

 survival, and differentiation of that cell. As long as this surface membrane is intact the 

 cell is protected. 



REFERENCES 



BUTSCHLI, O. . 1892 - "Untersuchungen uber mikroscopische Schaume und das Protoplasma. " Leipzig. 



CHAMBERS, R. , 1943 - "Electrolytic solutions compatible with the maintenance of protoplasmic structure. " Biol. Symp. 10:91. 

 CONKLIN, E. G. , 1933 - "Development of isolated and partially separated blastomeres of Amphioxus, " Jour. Exp. Zool. 64:303. 

 HOLTFRETER, J., 1943 - "Properties and functions of the surface coat in amphibian embryos. " Jour. Morph. 93:251. 

 HOLTFRETER, J., 1946 -"Structure, motility, and locomotion in isolated embryonic amphibian cells. " Jour. Morph. 79:27. 

 HOLTFRETER, J. , 1947 - "Observations on the migration, aggregation, and phagocytosis of embryonic cells. " Jour. Morph. 



80:25 and 57. 

 HOLTFRETER, J. , 1947 - "Changes of structure and the kinetics of differentiating embryonic cells. " Jour. Morph. 80:57. 

 LEWIS, W. H. , 1939 - "Some contributions of tissue culture of development and growth. " Growth Symposium. 1939. 

 ROUX, W. , 1894 - "Uber das Cytotropismus der Furchungszellen des Grasfrosches (Rana fusca). " Arch. f. Ent. Mech. 1:161. 

 SEIFRIZ, W., 1945 - "The physical properties of protoplasm. " Ann. Rev. Physiol. 7:35. 

 SIMON, P. , 1961 - "Association de blastodermes d'oiseaux en culture in vitro. Application de cett methode a la migration des 



gonocytes primaires d'un embryon, a un autre embryon". Coll. Int. du Centre. Nat. de la Recherche Scientifique. 



101:269-275. 

 TYLER, A. , 1946 - "Rapid slide making method for preparation of eggs. Protozoa, etc. " The Collecting Net 19. 



(See also sections on Culture of Isolated Anlagen, p. 218; Dissociation and Reaggregation of Cells, p. 224j and Tissue Culture 

 Techniques, p. 229). 



"A graduate from one of our larger universities, when asked why he changed 

 from Biology to Philosophy , said: "Well, I found that there was so much to be 

 learned in Biology tliat I had no time to think, so I took up Philosophy, where there 

 is nothing to be learned and I had all my time to think". 



E. M. East 



