22 ANTHOZOA HYDR01DA. 



But the life of the polypes considered abstractedly is proba- 

 bly in no instance coetaneous with the duration of the polypi- 

 dom, for the lower parts of this become, after a time, empty of 

 pulp and lifeless, and lose the cells inhabited by the polypes, 

 which, in an old specimen, are to be found in a state of ac- 

 tivity only near the summit, or on the new shoots. The Thui- 

 aria thuja affords a remarkable example of this fact ; the 

 branches which carry the polypes dropping off in regular 

 succession as younger ones are formed, so that the poly- 

 pidom retains, throughout its whole growth, the appearance 

 of a bottle-brush, the naked stem and the branched top 

 being kept in every stage in a due proportion to each other. 



SERTULARIA ABIETINA very common in July, and again in September, October, 

 and November : vesicles in September, but not plentiful. 



SERTULARIA FILICULA very common in July, when one specimen was found with 

 two vesicles : again plentiful in November, but the specimens looked younger, as 

 if of this year's growth, and one piece an inch and a half long was found rooted to 

 a skate's horny case ; which case, from its perfect state, must have been deposited 

 this year. 



SERTULARIA OPERCULATA very common ; vesicles in July, August, October, and 

 November. 



SERTULARIA ARGENTEA plentiful in September, and occasionally with vesicles, 

 but only young specimens. 



SERTULARIA CUPRESSINA only one, but a very beautiful specimen, loaded with 

 vesicles in August. 



THUIARIA THUJA plentiful and very fine in November; vesicles crowded the 

 latter part of November. 



ANTENNULARIA ANTENNINA dredged from deep water in August, very fine ; 

 thrown on the shore from August to November : no vesicles. 



PLUMULARIA FALCATA very plentiful the whole of autumn ; vesicles in July and 

 September, but not plentifully. 



PLUMULARIA PINNATA dredged up in August, very fine, above four inches high ; 

 vesicles abundant, but not full-grown : three specimens found on the shore in Sep- 

 tember, denuded of their pinnae, vesicles abundant : on one specimen they were 

 emptied of their ova, and the apertures had the circle of spinous teeth. 



PLUMULARIA SETACEA frequent on the roots of the Fucus digitatus, but not more 

 than an inch in height : vesicles in August. 



PLUMULARIA FRUTESCENS only one specimen, with one vesicle, in November. 



LAOMEDEA DICHOTOMA one or two poor specimens. 



LAOMEDEA GENICULATA very common. 



LAOMEDEA GELATINOSA small, on stones at low-water mark ; but thrown on the 

 shore in July about three inches long. 



CAMPANULARIA VOL UBILIS common ; vesicles in July and August. 



CAMPANULARIA SYRINGA rather common, twisting over the roots of Fucus digi- 

 tatus, and up the stems of Fucus sanguineus and Thuiaria thuja : no vesicles. 



CAMPANULARIA DUMOSA very plentiful and very fine in October and November. 



