ALCYONIDIUM. 37 



These animals are of the ordinary form, provided with about 15 ten- 

 tacula, whereof the cilia may be discovered by a magnifying power exceed- 

 in <r twenty diameters. The colour of the body is dark grey, but too 

 opaque to allow distinct inspection of the interior. Yet in an early stage, 

 and while the product is generating by diffusion in its native place, the 

 whole is so transparent, that, unless from the hydrse, its presence can be 

 scarcely detected. Without manifesting any peculiarities, they are viva- 

 cious and active. — Figs. 7, 8. 



On detaching a spot of this Alcyonidium from its site, the under sur- 

 face proves to be speckled with so many solid corpuscula-like darkish grains, 

 tending to spherical shape, and of irregular size ; fig. 9. Each of many 

 compartments is occupied by one or two. — Fig. 6. 



Propagation. — Among the modes of perpetuation incident to zoophytes, 

 two may be contrasted, one the formation of a new organic being, which 

 separates from the parent stock, to enjoy an independent existence, and 

 to found a family of its own. The other is by formation also of a new 

 being, which, instead of separating, remains in evolution, to augment the 

 number of living inmates, and to enlarge the dimensions of the parent 

 stock. It is by the preceding mode that a new colony among the Flustra 

 is founded, and by the latter, that mature specimens rivetted permanently 

 to their original site are extended. 



A small specimen of the Alcyonidium mytili was detached from a 

 mussel shell, which came off pretty clean, about the 2d of November. On 

 the 13th, portions were diffusing from two different parts of the circum- 

 ference, the smaller consisted of three new cells, disposed in a row, the 

 larger consisted of three rows of cells, the innermost comprising twelve. 



This latter portion, somewhat augmented next day, was delineated, 

 fig. 10, along with several of the hydrse, then displayed from the edges of the 

 older part of the spot, fig. 7. Now, the new cells, very distinct, seemed to 

 be pentagons, and almost all contained a dark coloured nucleus. — Fig. 10. 



On November 19, the generating margin of the spot or patch, fig. 3, 

 consisted of four rows of cells, fig. 11, when the nucleus, previously ob- 

 served, was clearly an embryonic hydra. Most of the cells, those of the in- 

 terior row excepted, were occupied by one, the body of which appeared a 



