LIMNOCNIDA TANGANICiE. 
95 
over that organ, and at certain regions have begun to grow 
up into the mass of ectodermic cells at the apex of the bud, 
thus indicating the position of the future tentacles, four of 
which are considerably in advance of the others. Some of 
the cells of the apical ectoderm arrange themselves round the 
forecasts of the endodermal axes of the tentacles, others, more 
deeply seated, arrange themselves in a single tier along the 
outer wall of the entocodon ; this causes a cavity to appear in 
the apical mass, separated from the cavity of the entocodon by 
the double row of ectoderm cells which becomes the velum of 
older medusas. The circular canal appears as a split in the 
endoderm at the base of the tentacles, aud is soon placed in 
communication with the enteric cavity of the parent by the 
four radial canals which arise one opposite to each of the four 
perradial tentacles. Between the radial canals and all round 
the entocodon the endoderm persists as the endoderm lamella. 
A noticeable feature in the development of the medusa- 
buds of Limnocnida is the entire absence of any trace of 
manubrium and mouth in any of the stages examined. The 
mouth probably breaks through at the date of the setting free 
of the young medusae. 
The only other account of the bud-formation of Limnoc- 
nida is that given by Moore in his book, ‘ The Tanganyika 
Problem/ He also describes the formation of the entocodon 
by invagination, but his account of the later stages differs in 
some respects from that given by Gunther. Thus, after 
describing the formation of the entocodon by a process of 
invagination he continues : “ Still later a second shallower 
invagination takes place forming the mouth of the bell, and 
within this the four primary tentacles are at fir§t folded 
inwards 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 cavity of the first 
ectodermal invagination of the bud, and quite visible from 
without. This is the rudiment of the manubrium of the bud. 
