J. D. Dana on Zoophytes. 191 
_ by continued budding: and why then should not the polyp form a 
tree, at least as well as the budding plant? This is in fact the 
true explanation of the formation of a zoophyte. An accumula- 
tion of polyps goes on by this succession of developments, and 
the same forms result as in vegetation—the tree, the» shrub, 
the lichen, cactus column, or sphere. 'The laws governing this 
process will be considered on a future page. We repeat here a 
former remark that this budding may and does take place inde~ 
pendently of coral secretions, as the secretion of coral is not an 
— * Palys) crass ‘Belonging to many of 
them 
bh The rt sentipligitted is isto: a saatihe of the Vidas 
process. 'The young polyp, after a short life of freedom, (a few 
days or less,) finds a place of attachment and then begins to bud, 
and by this means of multiplication, the stem rises, and branches 
are formed. The zoophyte is therefore a cluster of polyps, hav- 
ing generally an intimate connection with one another. ‘The an- 
Imals have each .a stomach, with tentacles and a mouth for con- 
veying food to it: but there is a free intercommunication of the 
fluids through the uniting tissues, by side pores or lacunes, and 
in some cases, even by the visceral cavities. It is precisely like a 
- thousand digestive sacs and mouths perpen ag to the nutriment 
of a single layer of animal tissue. 
~ 15. A still more singular mode of yeproduction, often the sub- 
ject of remark, ‘presents another striking analogy between the 
plant and the zoophyte :—the process of reproduction from arti- 
Jicial sections. It is well known that we may as easily raisea 
polyp from cuttings as a tree. Trembley and Baker* long since 
proved fully the title of the-Hydra to the name it bears; for the 
knife was unsparingly used, and only resulted in mul Shine Hy- 
dras.. They were cut into halves, and soon each was a perfect 
Hydra. One was divided into three parts, and in three or four 
days in summer, the tail had produced a head, the head a tail, 
and the middle part a head at one end and a tail at the other ; 
and even before completion, they sometimes began to give out 
buds. From forty parts as many Hydras resulted. The body slit 
© et Trembley, on Freshwater 2 fetote (iketecizes pour servira i histoire 
- @un genre de Polypes d'eau douce,) 1 vol. 4to., Leyden, 1744; and Phil. Trans., 
vol, Vili, of ‘the Abridgment, 1742. vont Bakr, A Natural History of the Pol. 
Ype, Svo. London, 1743. 
