22 ANTHOZOA IIYDROIDA. 



But the life of the polypes considered abstractedly is proba- 

 bly In no Instance coetaneous with the duration of the polypl- 

 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 Thul- 

 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. 



Sertucaria 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 foimd rooted to 

 a skate's homy 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 A-%ust. 



Thuiaria thuja — plentiful and very fine in November; vesicles crowded the 

 latter part of November. 



A.NTENNULARIA 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 iu 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 pinnse, 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 volubilis — 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. 



