DEVELOPMENT OF THE PHTLACTOL^MATOtlS POLYZOA. 505 



completed statoblast is now distinctly visible on the surface of 

 tlie disk, and exactly corresponds to the form of the secreting 

 matrix. 



It is thus evident that the cell-like chambers which compose 

 the float-ring are not true cells, but a chitinous deposit moulded 

 on the surface of cells. The statoblast is now complete, the soft 

 cellular layer which had surrounded it gradually disappears, the 

 epithelial layer which had held it to the funiculus also disappears, 

 and the statoblast falls into the body-cavity of the animal, where 

 it remains until the destruction of the latter sets it free. 



New Forms. 



Besides several new species belonging to genera already de- 

 scribed, a new generic form from North America has been added 

 by Hyatt to the Phylactolaemata. He names it Pectinatella. Its 

 nearest ally would seem to be Lopliopus, from which it differs by 

 its gelatinous ectocyst being confined to the base, where it forms 

 a broad disk, often several inches thick, and common to numerous 

 colonies. The naked endocyst is divided into lobiform branches, 

 in which the zooecia with their polypides are immersed. The pro- 

 trusion of the polypides is scarcely limited by any permanently 

 invaginated fold of the endocyst, as in LopTiopus and other genera, 

 the tentacular sheath in Pectinatella rolling out nearly to its full 

 length. This is described by Hyatt as resembling, in its completely 

 evaginated state, " a column supported by a simple ovolo and 

 fillet." The statoblasts are provided with marginal spines, as in 

 Cristatella. 



Only one species is known, P. magnifica, Hyatt. This occurs 

 abundantly in shallow water during the months of July and 

 August ; but as autumn advances it is found attached to logs in 

 deep cold water, at a depth which in some cases reaches 15 or 20 

 feet. " The tropical aspect and luxuriant growth of the clinging 

 masses, frequently several feet in diameter, investing the summits 

 of submerged stumps &c., are unequalled among the freshwater, 

 or even among the marine, forms of our climate." — Hyatt. 



LIXN. JOUEN.— ZOOLOGi', VOL. XIT. 



37 



