. Animal growth and development. Embryology; Growth; Biology; Growth; Embryology; Animals -- growth & development. 32 The Beginnings of Multicellular Organization REGULATION This term refers to the abihty of a morphogenetic system to turn out normal products of different absolute sizes. For example, individual frog embryos or tadpoles or adult frogs of a given species can vary markedly in size and yet be perfectly proportioned. That is, the sizes of the various parts (arms, legs, head, etc.) at each developmental stage bear precise relationships to the total length or total mass. Furthermo
. Animal growth and development. Embryology; Growth; Biology; Growth; Embryology; Animals -- growth & development. 32 The Beginnings of Multicellular Organization REGULATION This term refers to the abihty of a morphogenetic system to turn out normal products of different absolute sizes. For example, individual frog embryos or tadpoles or adult frogs of a given species can vary markedly in size and yet be perfectly proportioned. That is, the sizes of the various parts (arms, legs, head, etc.) at each developmental stage bear precise relationships to the total length or total mass. Furthermore, if cells are surgically removed from a very young frog embryo, the remainder will develop into a very tiny but nonetheless normal tadpole, again demon- strating the same relationship of parts to whole. Slime molds also display regulatory capacities. For example, myx- amoebae packed together in a solid mass produce relatively large migrat- ing slugs and fruiting bodies; some are as much as 5 mm in length and contain hundreds of thousands of cells. If sparsely distributed, the myx- amoebae form tiny slugs and fruits a few tenths of a millimeter in length that contain a few hundred cells. Yet the gross proportions and the rela- tive amounts of cells comprising the various parts of the fruiting body remain the same. This regulatory capacity is exhibited at a truly startling. Fig. 16. Two views of a fruiting body formed by the "fruity" mutant of D. discoideum. This highly or- ganized multicellular struc- ture consists of 9 spores, 2 stalk cells, and I basal 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 Sussman, Maurice. Englewood Cliffs, N. J. , Prentice-Hall
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