the centre, and fused, Fig. 24. In this ^vay the lumen of the 

 oesophagus is divided into four tubes (oe. t. Fig. 24) repre- 

 senting the grooves that v/ere present in its armies in the ear- 

 lier stages. In this case the fusion at the centre has gone 

 so far as to involve the edges of the lips and the labial 

 grooves of the different pairs of arms are not in open communi- 

 cation but a short cross -shaped tube connects them at the cen- 

 tre and the oral disk is no'.v completed. j 

 j It is interestir^_$ to note that Claus has found a stage 

 both in Pilema and in Cotylorhiza that, while showing the char- 

 jacteristic family differences, as also a certain resemblance 

 Ito this stage in Cassiopea. In all three, the walls of the 

 proboscis have fused so as to divide its lumen into tubes and 

 the formation of oscula has begun at the tips of the arms in 

 such a way that we have on each arm three oscula with a ves- 

 icle in the angles between them. The occurrence of this 

 stage in the ontogeny of three so distinctly separated families 

 imust have some morphological significance and we may regard 

 these eight primary vesicles as homologous in the three groups. 



! The mode of fonnation of tlie oral funnels becomes evident 



I 



at this stage. They are not formed in Cassiopea simply by a 

 series of fusions of the lips along the line of the labial 

 groove, as Hamann found (1882) to be the case in CotyloT'hiza(?) . 



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