JOHN H. PHILLIPS 249 



m 







Fig. 3. Twelve-day-old clone of cells from A. elegantissima. 

 Stained with periodic acid Schiff's. Magnification 900x. 



peculiarities, some of which it is hoped may be corrected through 

 the use of a better nutrient medium. Suspensions of single cells 

 obtained either directly from animals or from cultures do not 

 show reaggregation. On the contrary, a developing clone generally 

 shows outgrowth and separation of cells from the growing center. 

 The separated cells occasionally move a short distance before 

 becoming new centers of growth. 



Figure 3 shows a twelve-day-old clone developing on a cover- 

 slip. The preparation was fixed in methanol and stained with 

 periodic acid Schiff's stain (5). The cells are filled with a granular 

 material that makes observation of the nucleus very difficult. These 

 granules, when observed in living cells by phase contrast micros- 

 copy appear as barred objects resembling mitochondria. Similar 

 intracellular structures can be observed in suspensions of cells 

 obtained directly from the animal, but such cells do not show as 

 high a concentration of these objects. When these cultured cells 

 are removed to artificial sea water containing ethylenediamine 

 tetraacetic acid (EDTA), they rapidly change their appearance to 

 that shown in Figure 4. The addition of sodium acetate to 0.1% 

 Edamine medium appears to produce a similar effect which is 

 under investigation at the time of this writing. Until the concentra- 



