1896] MICROSCOPICAL JOURNAL 295 



The bad is now ready to begin its free existence as a 

 medusa; and by a few vigorous contractions, breaks its 

 connection with the manubrium and passes out at the 

 end of the calycle. In the very act of extrusion, its 

 disk expands and the tentacles unroll, so that, by the 

 time the medusa is free from the calycle, it is fully ex- 

 panded and begins at once the act of swimming. At birth 

 the medusa, has sixteen tentacles (fig. 12, a) of which 

 one is opposite each of the four radial canals and three 

 others are arranged at equal distances in each space be- 

 tween any two of these four. There is the sub-umbrella 

 cavity (g) in the centre of which is the proboscis (e) and 

 in the centre of this we find the mouth (d) which opens 

 into the stomach — a four-sided digestive cavity, from 

 each corner of which a radial canal (b) extends outward. 

 These canals extend nearly to tlie edge of the disk, where 

 they connect with the circular canal (c) which passes 

 through the entire circuit of the margin. Through these 

 canals a constant circulation of water is kept up by 

 means of large vibratile cilia There are also eight 

 otocysts (f) at the bases of the eight tentacles which 

 stand one on each side of the four radial canals. They 

 are circular in outline and contain in their centre a highly 

 refractive body. As to the development of these I was 

 able to make out practically nothing. 



The development of the Campanularian medusa resem- 

 bles in many respects that of the Tubularian medusa. 

 This is evident from a comparison of these figures with 

 those by Korschelt and Heider in their Text Book of 

 Embryology, fig. 16. The sub-umbrella cavity of the one 

 is formed in almost identically the same way as the 

 bell-cavity of the other. The same is also true of the 

 radial canals, the circular canal, the proboscis, and the 

 stomach. The important diff"erence in the development 

 of the two is the gradual change in the form of the 



