THE TANGANYIKA PROBLEM. 



3°3 



small knobs, these knobs being, in reality, the initial rudi- 

 ments of future medusoid buds. As the season advances 

 such rudiments go through a rapid metamorphosis, they 

 become definite hollow evaginations leading from the gas- 

 tric cavity. The little pouches thus formed thicken at their 

 apices, and an invagination of the ectoderm of the manu- 

 brium takes place at these points, each invagination becom- 

 ing cut off from the exterior. The ectodermal lining of 



tig- 3- — Semi-diagramatic representation of the formation of asexual buds of the 

 Tanganyika medusa. The thick black line is the endoderm. 



these cavities becomes the ectoderm of the interior of the 

 bell and the manubrium of the growing bud, as well as 

 forming the inner surface of the imperforate velum. Still 

 later a second, shallower invagination takes place, forming the 

 mouth of the bell, and within this the four primary tentacles 

 are at first folded inward towards the centre of the velum. 

 About this time the endodermal lining of the parental 

 manubrium (which projects into the bud from its gastric 

 cavity and forks into four radial canals) becomes thickened 

 and folded, so as to form a rounded boss projecting into the 



