THE freshwater Bryozoan Pectinatella magnifica produces, as is well known, lenticular statoblasts or winter buds that carry at the margin hooks whose number varies from 11 to 26. The statoblasts develop in the funiculus of the zooids. The zooids arise by budding from embryonic tissue which is laid down even in the statoblast-embryo of the preceding generation. The zooids of a colony are thus related as closely as possible, being developed parts of one and the same germplasm. The zooids of a colony are found in branches or twigs that radiate from a center and, in Pectinatella, are thick, short and blunt, forming a stellate colony. Many of these corms lie in contact with each other on the surface of a more or less spherical mass of jelly that is secreted by the colony. The colonies are in close contact like the facets of a compound eye. As the gelatinous mass increases so does the area available for the colony and thus additional space is allowed for their growth. Whence come the colonies that lie on the surface of any one of the gelatinous masses? In part they arise by fission of preexisting colonies. A given colony gains an elliptical shape and then constricts in the short axis; the periphery of the colony is increased and room made for new branches and new young buds. If all colonies on the surface of a given mass arose thus we could refer the origin of them all to the original colony that came from the statoblast. But, unfortunately, things are not so simple. For two statoblasts may germinate in close proximity to each other on the same substratum and, under such circumstances, the masses of jelly they secrete will flow together and form parts of a single mass. Thus the gelatinous masses in nature are of two sorts: