We may call it the Blastaea. Its body consisted, when fully formed, of a simple hollow ball, filled with fluid or structureless jelly, with a wall composed of a single stratum of ciliated cells. There were probably many genera and species of these blastaeads in the Laurentian period, forming a special class of marine protists.
There are "blastaeads" of this kind even among the Protophyta the familiar Volvocina, formerly classed with the infusoria. The common Volvox globator is found in the ponds in the spring a small, green, gelatinous globule, swimming about by means of the stroke of its lashes, which rise in pairs from the cells on its surface.