THE TANGANYIKA PROBLEM. 299 
stiffly arrayed above the bell in the manner represented in 
Fig. 1. It is a truly pelagic form, being often encountered 
in the deep open water of Lake Tanganyika, where it is 
seen slowly pulsating at all depths, and during life is so 
glassy as to be almost invisible. Its chief anatomical peculi- 
arities are constituted by the broadness and shortness of the 
Fig. 1. — Living asexual adult of the Tanganyika 
medusa, enlarged about one-third. To the right 
is seen a string of buds becoming detached. 
manubrium, the diameter of which is generally about two- 
thirds that of the whole disc. It is also so short that, when 
the animal is alive, it does not project beyond the velum. 
In association with these peculiarities we have a great 
development of mesoglea, forming the large lens-shaped 
mass that partially fills up the gastric cavity, and which, by 
its transparency, gives the organism the form of a ring 
