396 THE FORMS OF CELLS [ch. 



partial vortex suspended by a thread or column — just as in Over- 

 beck's jet-experiments; and the figure so produced, in either case, 

 is closely analogous to that of a medusa or jellyfish, with its bell 

 or "umbrella," and its clapper or "manubrium" as well. Some 

 years ago Emil Hatschek made such vortex-drops as these of hquid 

 gelatine dropped into a hardening fluid. These " artificial medusae " 

 sometimes show a symmetrical pattern of radial "ribs", due to 

 shrinkage, and this to dehydration by the coagulating fluid. An 



Fig. 121. Various medusoids: 1, Syncoryne; 2, Cordylophora; 

 3, Cladonema (after Allmaii). 



extremely curious result of Hatschek's experiments is to shew how 

 sensitive these vorticoid drops are to physical conditions. For using 

 the same gelatine all the while, and merely varying the density of 

 the fluid in the third decimal place, we obtain a whole range of 

 configurations, from the ordinary hanging drop to the same with a 

 ribbed pattern, and then to medusoid vortices of various graded forms. 

 The living medusa has a geometrical symmetry so marked and regular 

 as to suggest a physical or mechanical element in the little creature's 

 growth and construction. It has, to begin with, its vortex-hke bell 

 or umbrella, with its cylindrical handle or manubrium. The bell is 



