248 



THE BIOLOGY OF HYDRA : 1961 



.♦ .•> 







Fig. 2. Clones of A. elegantissima growing on the side of a test tube. 

 Magnification 129x. 



single cells is generally made difficult by the slight movement of 

 cells over the surface of the glass. Therefore, cloning procedure 

 of Puck (7) is generally used. Cells are mixed w^ith 10 ml. of 

 nutrient medium containing 0.2 /y agar, and the mixture is placed in 

 a Petri dish containing a layer of 1% agar in artificial sea water. 

 Developing clones are observed as clusters of cells that are generally 

 separated from one another by a distance equal to the cell diameter. 

 Development from a four through a thirty-two cell stage can be 

 observed. The generation time is somewhat in excess of twenty- 

 four hours. The clone can be removed with a capillary pipette 

 and transferred to fresh nutrient solution. Because of the dis- 

 tinctive appearance of a developing clone, there is no difficulty in 

 avoiding clumps of cells which were present in the inoculum. 

 The appearance of the cells growing in vitro shows certain 



