SERTULARIA. 209 



Plate XXXIX. fig. 18., Serrate vesicles, producing a yellow planula. 

 Fig. 19., Nascent Sertularia from the planula. 



Amidst considerable embarrassment on the subject, the preceding, 

 combined with other observations, seem to warrant the following conclu- 

 sions : — 



I. That there are two distinct species of the Sertularia antennina of 

 the older authors. 



II. That the Sertularia antennina of the Linntean system, the modern 

 Antennularia indivisa, appears as a single ruddy stalk, ten inches high, 

 begirt by slender verticillate twigs, and bearing axillary ovate vesicles, 

 each containing a single yellow planula. 



III. That the Sertularia antennina of the same system comprehends 

 also a greenish shrub, diverging into boughs and branches, clothed with 

 twigs : likewise with slender, prolonged, plumose vegetations sometimes 

 interspersed, whereon, besides hydra?, are borne long, ampullate, axillary 

 vesicles, each containing many planulse. 



IV. That three vesicles, all different from each other in form, may 

 appear on the latter, the Sertularia ( Nemertesia) ramosa. 



V. That vigorous reproductive energies reside in the Ramosa, which 

 are readily and frequently exhibited : while similar energies are feeble and 

 rare in the Antennina indivisa or Lobster's Horn. 



Plate XXXIX. 



Fig. 1. Sertularia antennina (Antennina indivisa — Nemertesia Antennina), 

 Lobster's Horn. 



2. Twig with hydrse. 



3. Section of a stalk with a vesicle. 



4. Section of a stalk with vesicles. 



5. Planulse from the vesicle. 



6. The same enlarged. 



7. Sertularia (Nemertesia) ramosa. Twig with hydrse. 



8. Section of the stem. 



9. Plumose prolonged twig, with hydrse and axillary vesicles, enlarged. 

 VOL. I. 2d 



