228 
THE OCEAN WOULD. 
plant, which throws out its slender steins in all directions, covering all 
the neighbouring ground. 
The young Medusa lives some time under this form. Then one of 
the polypes becomes enlarged and its form cylindrical. This cylin- 
der is divided into from ton to fourteen superposed rings. These 
rings, at first smooth, form themselves into festoons, and separate into 
bifurcated thongs ; the intermediate lines become channeled. The 
animal now resembles a pile of plates, cut round the edges. In a 
short time each ring is stirred at the free edge of its fringe: this 
becomes contractile. The rings are individualised. Finally, these 
annulaj creatures, obscure in their lives, isolate themselves. When 
detached, they begin to swim : from that time they have only to 
perfect and modify then form. From being flat, they become concave 
on the one side and convex on the other. The digestive cavity— the 
gastro- vascular canals — become more decided; the mouth opens, the 
tentacles are elongated, the floating marginal cirri become more and 
more numerous ; and now, after all these metamorphoses, the Medusa 
appears : it perfectly resembles the mother. 
TuBULAEIDiE. 
We have already said that recent researches have led to a separation 
of a class of animals from the Sertularia, and to then being united 
with the Medusae. Of these creatures we formerly only knew one ol 
the forms, namely, tho polype form ; or, rather, the first stage of d- 
During their earliest days they possess a polypier, furnished with ten- 
tacles, and a hell-shaped body. During their mednsoid age, they present 
a central stomach, with four canals in the form of a cross, and four 
to eight tentacles with cirri. Tho animals constitute the Tubular id®, 
comprehending many genera ; among others the Tubularia and Cani- 
panularia, hi studying which Yan Eenedcn of Louvain discovered most 
interesting facts connected with the subject of alternate generation. 
Tho class of zoophytes ranged among the Tubularia have the power 
of secreting an inverting tube of a horny nature, in which the fleshy 
body can move up and down, expanding its tentacles over the top- 
Others of them give forth buds, each of which takes the form of a 
polype, and these, being permanent, give it a shrub-like or branched 
