THE TANGANYIKA PROBLEM. 301 



the Lake. In the south there is a long dry season lasting 

 from May to September, then a short wet season lasting for 

 some two or three weeks, then a spell of fine weather which 

 usually continues till about the end of November, when the 

 great rains begin, and these finally terminate in a succession 

 of heavy thunderstorms and furious nocturnal gales during 

 the early days of May. In the north, that is in latitude 3 30' 

 south, the seasons are more equal ; the September rains 



Fig. 2. — Living sexual adult of the Tanganyika 

 medusa, showing the character of the manu- 

 brium. 



begin sooner and last longer, while the long rains of the 

 south are proportionately shortened, so that in this portion 

 of the lake we really experience the true climate of the 

 equator, where there are two short wet seasons and two 

 short dry seasons, the rains occurring whenever the sun 

 passes overhead on its way north and south. 



The jelly fishes, however, do not differ in the phase of 

 their life cycle in different parts of the lake, and conse- 

 quently it is really incorrect to say that their metamorphosis 

 corresponds in any way directly with the seasons. 



