United States or Ukraine ? Vote for the TOP Country of the Week !
In Prophysema the primitive gut is a simple oval cavity, but in the closely related Gastrophysema it is divided into two chambers by a transverse constriction; the hind and smaller chamber above furnishes the sexual products, the anterior one being for digestion. The only material difference between them is that in the sponge the thin two-layered body-wall is pierced by numbers of pores.
When these are closed they resemble the Physemaria. Possibly the gastraeads that we call Physemaria are only olynthi with the pores closed. Prophysema primordiale, a living gastraead. The same in longitudinal section. Ascula of gastrophysema, attached to the floor of the sea. Olynthus, a very rudimentary sponge. The lowest form of the Cnidaria is also not far removed from the gastraeads.
Word Of The Day