VAUIATION IN A JELLYFISH. 



1047 



Limnocnida being another African lacustrine form is of 

 particular interest. Giinther found that out of 70 individuals 

 collected by Dr. Ounnington in Lake Tanganyika, 54 medusae 

 showed the typical number (four) of radial canals, whilst 16, or 

 24 per cent., had five or more ; as in the case of Moirisia, specimens 

 Avith five radial canals were commoner than those with a larger 

 number. Giinther, however, found no medusoe with only three 

 canals, but such trimerous forms have been described in other 

 genera, e. g. Podocorpie [8] and Ratltkea [7]. 



Text-fi^. 222. 



C D 



Diagrams to sliow tlie arriingement of the tentacles in four medus». 

 B represents the normal tetramcrous form. 



Similar variations occur in several membere of the Scypho- 

 medusiB : perhaps the most complete account of the phenomenon is 

 that given by E. T. Browne for Aurella aurita [11, 12J. This 

 author examined the variation in the number of tentaculocysts 

 in the ephyra larvte and adults of the jelly-fish, and found that 



71* 



