194 J. D. Dana on Zoophytes. 
to the occurrence of eggs in the larves of imperfect young - 
insects. 
Artificial sections may be considered another means of re- 
production.. The process however depends on the same cause as _. 
that of budding—the absence of a concentrating nervous system: 
it matters little whether the fragment remains as a part of the 
parent, or be detached from it. : 
18. The facts which have been jiitesitads indicate a ote 
siabsdivinion of Zoophytes into two groups or orders, as follows: 
. Hyprormea. Visceral cavity,.a simple tube; reproductive 
Feuations residing in the general walls of the cavity youns, or 
ova pullulating from the sides of the parent. 
IL Acrrvomea. Visceral cavity divided veitidnity by fleshy 
lamella ; reproductive functions belonging to the margin of the 
fleshy lamella ; young or ova set free in the visceral cavity, 
and escaping freer it by Sere up through the — out of 
the mouth. 
The Hydroidea are small s pected, sometimes fctenibe cornet; 
but never calcareous coralla, and contributing nothing essentially 
to reefs: The name is derived from Hydra, one of the included 
genera. 'The order Actinoidea comprises all the, ordinary reef- 
forming Zoophytes, together with the Actiniz and allied species. 
The name is from Actinia, which comes from the Greek «zt, 4 
ray of the mats and alludes to the radiate flower-like summit.* 
he characters given exclude the Bryozoa, a "group embracing, the Flustras 
Sed Cellepores. Their relations to zoophytes are briefly explai ained in the last 
volume of this Journal, page 287: They have an intestine, which curves back . 
and terminates in an anus near the mouth, and in this and’ other respects differ 
from true zoophytes, as we have used this term 
Zoophytes pass into the class Acalephe Shrovgll the Actinecta on the ae 
the former, and the Porpite and the Velellz on the part of the latter, which-are 
all floating oceanic species, and have. nearly similar tentacles about a ce entral | 
mouth. Passing beyond these species, the structure of the Acaleph varies wide- 
ly from the Actinoidea; the internal cavity, the germinal system, tentacles, and 
ee habit, becoming very different. The Hydre closely resemble the young 
of certain A eahephs; and have been lately classed with the Acalephz, especially 0” 
account of the structure of their tentacles, which are furnished with minute dart- 
peering or filiferous sacs. (See Dujardin, Ann. des Sci. Nat., iy., 1845, p- 208.) 
es are also excluded; if animal, they have little in common with 
zoophytes excepting their plant-like forms and the most general properties of a0- 
Ae inct animals allied in any way to polyps have ever been de- 
Of recent authors, Grant, Audouin, Milne Edwards, Bowerbank, Dujar- 
1d Laurent, consider sponges as animal; while Link, Blumenbach, Owen, 
Johnston, are inclined to place ‘them in the sae kingdom. 
