. Biology. Biology. CELL AGGREGATES 77 parent; both parent and offspring then reproduce in the same way until a branching tree-like colony results (Fig. 31). Sphaeroidal colonies, finally, differ from the others in that the cells resulting from division remain embedded in a gelatinous matrix secreted by the parent organism (Fig. 24). Such colonies are usually spherical, the constituent cells being ar- ranged about the periphery. When this condition in develop-. FIG. 31.—An arboroid colony of flagellated protozoa, Codosiga cymosa, Sav. Kent. (From Calkins after Kent.) ment is reached it is not
. Biology. Biology. CELL AGGREGATES 77 parent; both parent and offspring then reproduce in the same way until a branching tree-like colony results (Fig. 31). Sphaeroidal colonies, finally, differ from the others in that the cells resulting from division remain embedded in a gelatinous matrix secreted by the parent organism (Fig. 24). Such colonies are usually spherical, the constituent cells being ar- ranged about the periphery. When this condition in develop-. FIG. 31.—An arboroid colony of flagellated protozoa, Codosiga cymosa, Sav. Kent. (From Calkins after Kent.) ment is reached it is not a long step to the simplest type of metazoan, and we find cases where there is even a regional dif- ferentiation in the colony. A Proterospongia, for example, is a gelatinous mass with cells arranged about the periphery; when abundantly fed these cells migrate one by one to the in- terior of the jelly mass, losing their flagella in the process. Within the jelly they divide, and the cells then wander back to the periphery to take their place with the feeding cells of the colony. Here then is a temporary differentiation into vegeta-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Calkins, Gary N. (Gary Nathan), b. 1869. New York, H. Holt and company
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