OBSERVATIONS ON POI.YZOA. 209 



waterlogged timber, are unequalled among the fresh-water, 

 or even among the marine Saccata of our climate. 



The communities, assembled in countless profusion up- 

 on the gelatinous ectocyst, are crowded together and being 

 compressed become irregularly hexagonal in their outlines. 

 The polypides upon the lobiform branches, adorn the bor- 

 ders of these hexagonal patterns with a dense, glistening 

 fringe, speckled with the scarlet coloring of their oral re- 

 gions ; and the bare coenoecial trunk (PI. 9, figs. 5, 6, 7, A') 

 in the centre shine with a deep, opaline lustre, completing 

 the rich, coralline effect of the fringed outlines. 



The protrusion of the polypides is not limited by the in- 

 vaginated fold, as in the preceding genera, but they roll out 

 nearly the full length of their evaginable endocyst, and re- 

 semble columns supported by a simple ovolo and fillet 

 (Pis. 10, 12). The fillet corresponds to the invaginated 

 fold of the preceding genera, and the ovolo-likebend in the 

 endocyst is produced by the contraction of the anterior re- 

 tentor muscles. 



In July and August specimens of Pectinatella magnifica 

 are very abundant in shallows and in the depths of Pen- 

 nissewasse pond, but as the fall advances, those in the 

 shallows die, and in October they can live only upon the 

 logs in deep, cool water, or in shaded situations. These 

 autumnal specimens are old, and being unable to with- 

 stand the direct rays of the sun, disappear from all exposed 

 positions, where they grow with impunity as strong and 

 healthy adults earlier in the season. I have found them 

 fifteen or twenty feet below the surface, showing a marked 

 departure in this respect from the preceding genera, whose 

 species seldom occur below two, or three feet, and are al- 

 most invariably near the shore line. 



CEISTATELLA, 



The Cristatellae are by far the most highly organized, 

 not onlv of the Phylactolsemata but of all the Polyzoa 

 (Pis. 13," 14). 



The ccencecia are neither dendritic, as in Fredericella 

 and the Plumatell*e, or lobate, as in Lophopus and Pec- 

 tinatella, but naked, depressed sacks, capable of determi- 



