166 TOILERS IN THE SEA. 



and divided, forming the rudiments of the radiating 

 base, and the whole structure is soon invested in a 

 chitinous sheath or elementary polypary. In the 

 course of time, as growth proceeds, the upper end of 

 the attached embryo developes into a fixed polype, 

 enclosed within a capsule, with a moveable lid, which 

 is pushed off when the animal is mature. Then the 

 initial step is complete, and the first individual, which 

 for the time being constitutes the entire colony, is 

 perfected ; from this unit, by a series of successive 

 buddings and branchings, the plant-like colony is gra- 

 dually built up, in all respects resembling the .parent, 

 from whence the solitary embryo fell into the water, 

 or was cast out into the world of waters, to make a 

 home for itself, but a short time previously. And, in 

 like manner, every polypary, with its hundreds of 

 individuals, commenced, in such humble guise with a 

 single polype. 



Dr. Johnston has thus summarised what was 

 known, in his time, of the growth of the polypary : 

 " The ripe ovule, or bud, discharged from its matrix 

 settles, and fixes itself to the site of its future ex- 

 istence, by minute fibres, which pullulate from the 

 under side, while, from the opposite pole, a papillary 

 cone shoots up to a height determined by the law 

 which regulates the peculiar habit of the species. 

 The upward growth is then arrested, and the apex 

 becomes enlarged and bulbous. The structure of 



