. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEVELOPMENT OF BOTRYLLUS BUD 181 elude other cells from the first. No stage, with the possible exception of those shown in Fig. 3, has been seen in which the ova proper are without accessory cells. These cells are of two kinds, a few flattened follicle cells clinging to the surface, and an equally small number of nurse cells completely within the cytoplasm of the ovum. Following multiplication, the outer surface cells become columnar, as in Fig. 6, D, and eventually flatten again as they give rise to the egg chorion. The nur

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. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEVELOPMENT OF BOTRYLLUS BUD 181 elude other cells from the first. No stage, with the possible exception of those shown in Fig. 3, has been seen in which the ova proper are without accessory cells. These cells are of two kinds, a few flattened follicle cells clinging to the surface, and an equally small number of nurse cells completely within the cytoplasm of the ovum. Following multiplication, the outer surface cells become columnar, as in Fig. 6, D, and eventually flatten again as they give rise to the egg chorion. The nurse cells also multiply and are clearly involved in the growth of the ovum. They are eventually extruded into the perivitelline space as the. 18 days FIG. 7. Growth curves for linear growth of bud, and of single egg X 10. On the same chart is also shown a cleavage curve indicating the geometrical increase in cell number associated with growth. inner follicle cells or "test" cells of the mature ovum (cp. Berrill, 1929). Thus the development of the gonad as a whole is a comparatively complex process. Yet the ova and spermatozoa attain actual functional maturity at virtually the same time and almost at once after the bud as a whole has become active. Either some factors external to the gonads suddenly terminate growth and multiplication and enforce final differen- tiation to coincide with that of the rest of the bud, which is unlikely, or the development has from the first been approaching a condition of equilibrium permitting final cyto-differentiation. That this last is the. 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 work.. Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richa