208 HYATT, 



their length. The polypide, also, is capable of more ex- 

 tended protrusion, and its motions, therefore, are less re- 

 strained. The arms, previously indicated in the lopho- 

 phore of Fredericella, are fully developed, and stretch out 

 on the dorsal side just above the anus, giving a crescentic, 

 or horse-shoe shaped aspect to the disk, which is retained 

 throughout the succeeding genera. 



The ectocyst may be either transparent or brown in the 

 same species, and the polypides may be widely separated, 

 as in Fredericella, or be closely aggregated, the branches 

 and cells adhering together by means of their gelatinous 

 ectocysts. 



L0PH0PUS. 



Lophopus introduces us to a new class of characters. 

 The ectocyst, in place of being a thin enveloping sheet, is 

 a thick deposit of clear jelly in which the coencecium is 

 buried. The branches are lobiform, and the cells even less 

 widely separated, or differentiated, than in the aggregated 

 varieties of Plumatella. 



Prof. Allman describes Lophopus crystallinus as attach- 

 ed to the stems of Lemna, and other fresh water plants, 

 but avoiding exposure to bright sunlight. 



These positions must necessarily, however, be less shad- 

 ed than those occupied by the majority of the Plumatellae. 



PECTItfATELLA. 



The reproductive and vital energies of the group reach 

 their climax in the voluptuous beauty and endless multi- 

 plication of the ccenoecia in Pectinatella (Pis. 9, 10, 11, 12). 



The cells of the separate polypides are wholly merged 

 in the lobiform branches, and the gelatinous ectocyst, often 

 several inches thick, is gathered underneath the coencecia 

 (PI. 9, fig. 5, D). It affords a common base for all the 

 colonies, and is no longer, as in the preceding genera, con- 

 fined to one ccenoecium. 



The tropical aspect and luxuriant growth of the cling- 

 ing masses, frequently several feet in diameter, investing 

 the summits of submerged stumps, and the branches of 



