162 ZOOPHYTES. 



orifice of the cell opens simply from it, without any tubular prolongation. 

 A white hydra, with about 19, and sometimes a greater number of tenta- 

 cula, deeply muricate, protrudes its long neck from the cell. — Fig. 15. 



Two kinds of vesicles have been observed on this Sertularia, — the one 

 ovoidal, fig. 18, — ^having expelled its abortive contents ; the other globu- 

 lar, fig. 20. The contents of the ovoidal vesicles are white or yellow. 

 Some faint yellow planulse have issued from the former, on the first of 

 August, which offered nothing remarkable. — Fig. 21. The contents of the 

 globular vesicles are yellow. No semblance of circulation could be dis- 

 covered in the hydra. 



A powerful vegetative faculty resides in the stem, insomuch that a 

 prolongation, shooting down from a section, has been rooted in a night. 



Much irregularity pervades this species, of which diiFerent specimens 

 exhibit varied aspects, in the number and dimensions of the parts, as well 

 as in the number and distribution of the vesicles. Sometimes one or two 

 of the latter appear at a remote interval : sometimes several are closely 

 huddled together, on or about the stem. 



The facility of obtaining the product, however, renders it a conve- 

 nient subject for observation. 



Plate XXVI. 



Fig. 14. Sertularia pumila. 



15. Specimen with ceUs and hydrse, enlarged. 



16. Articulation consisting of two cells. 



17. Ovoidal vesicle discharging its abortive contents. 



18. Empty ovoidal vesicle on an articulation. 



19. Specimen with globular yellow vesicles, 



20. The same, enlarged. 



21. Planulse from ovoidal vesicles. 



All the figures except 14. and 19. are enlarged. 



§ 6. Sertularia Halecina and Cognates — Herring Bone Coralline. 

 Plates XXVII. XXVIII. XXIX. XXX.— It appears to be very obscure 

 what is the true Sertularia halecina specified in the Linnsean Systema 



