50 POPULAR HISTORY OF THE AQUARIUM. 



motion to such a degree as enabled them to change their 

 form bj protruding certain portions of their outline ; others 

 were contracted into a globule^, fixed and changeless,, with the 

 matter produced in the form of a creeping rootlet/^ 



" The next stac^e that I observed was that in which the 

 adherent mass had become shelly, as I presume ; for the mar- 

 ginal portions were perfectly transparent and colourless, and 

 the opaque granular matter had retired to the centre, where, 

 irregular in form, it had given rise to a tube. This tube 

 had already formed one joint : its extremity was closed 

 and rounded, and had not yet begun to dilate into a cell. 

 The medullary matter proceeding from the granular mass at 

 the base, passed through the lower portion of the tube as 

 a central cord, but completely filled the terminal moiety. 

 Another specimen had proceeded so far as the formation of 

 the cell, the bottom of which was filled with the granular 

 matter, as yet amorphous, no trace of the polype being yet 

 discoverable. This was the most matured phase of the 

 development that appeared on the experimenting plates of 

 glass ; but the transition from this state to that of the young 

 polypes, already described, at the bottom of the vessel, is 

 short and obvious ; and the progress from one of them to a 

 perfect polypidom is a matter of increase and aggregation. 



