SERTULARIA. l75 



Plate XXXI. 



Fig. 1. Sertularia (Thoa) Beanii. 



2. Hydra. 



3. Branch with twigs and frills. 



4. Branch with vesicles. 



5. Hydrse, and prolific vesicle. 



6. Prolific vesicles. 



7. Planulae about to quit a vesicle by the orifice a. 



8. Planula liberated. 



9. Planulse metamorphosing. 



All the figures except fig. 1, enlarged. 



§ 7. Sertularia muricata. — Plate XXXII. — In a depauperated 

 state, the resemblance of this product to the Sertularia halecina is such, 

 that we are prone to number it among the cognates ; nor, until the pecu- 

 liar substances which naturalists have denominated vesicles be proved pro- 

 lific, do I feel altogether disposed for its exclusion. 



The Sertularia muricata rises four or five inches high, by a stem com- 

 posed of aggregated tubuli. Its boughs, branches, and subordinate parts, 

 all diverge from each side of their principals in alternate arrangement. — 

 Plate XXXII. fig. 1. The hydra, provided with about 22 or 24 muri- 

 cate tentacula, issues from the tubular extremity of a twig distinguished 

 by frills, whither it seems to have only a partial retreat, fig. 2. The stem 

 of the adult specimen is brown ; the hydra is green ; and the whole pA»- 

 duct presents quite the character of the Sertularia halecina exhibited in 

 Plate XXVII. 



Various parts of this zoophyte, in its better state, are invested by pe- 

 culiarly formed capsules or vesicles, cotemporary with the living hydra, 

 and sometimes in vast profusion. Perhaps they exceed the multitude of 

 the vesicles proper to other Sertulariac, nor do they seem restricted to any 

 particular part. The stem is often entirely covered by clusters huddled 

 together in confusion. 



This inorganic substance, if it be a vesicle, somewhat resembles a 

 flattened filbert, attached by the shortest pedicle to the stem or branches 



