. A manual of zoology. Zoology. Fig. 178.—Diagram of sections of (.4) a poh-p and (B) a medusa. cJ, ectoderm; ek', of exumbrella; ek~, of subumbrella; ek^, of manubrium; el, endoderm (cathamnal) layer arising from ol^Literation of digestive space; en, entoderm; r, ring canal; 5, sub- umbrella; (, tentacles; v, velum; -v, supporting layer (gelatinous in B). it produces sexual individuals (medusa?) which separate and swim away. Since polyp and medusae are morphologically comparable, before the escape of the medusa the colony is polymorphic, consisting of individuals (hydranths) which reproduce o
. A manual of zoology. Zoology. Fig. 178.—Diagram of sections of (.4) a poh-p and (B) a medusa. cJ, ectoderm; ek', of exumbrella; ek~, of subumbrella; ek^, of manubrium; el, endoderm (cathamnal) layer arising from ol^Literation of digestive space; en, entoderm; r, ring canal; 5, sub- umbrella; (, tentacles; v, velum; -v, supporting layer (gelatinous in B). it produces sexual individuals (medusa?) which separate and swim away. Since polyp and medusae are morphologically comparable, before the escape of the medusa the colony is polymorphic, consisting of individuals (hydranths) which reproduce only asexually and of others which have taken over the sexual reproduction (medusa;). Hence alternation of. Fig. 179.—Comparison of a medusa and a sporosac (orig.). A, fully developed medusa; B, medusa with the manubrium closed, still attached to the blastostyle; C, medusa reduced to a simnle manubrium (sporosac); D, last stage, eggs being produced in the body wall {Hydra). generations has arisen here from a division of labor or polymorphism of individuals originally of equivalent value, in which some individuals (the sexual) have separated and acquired a peculiar structure. While alternation of generation has arisen from polymorphism, it can again produce it. This occurs when the medusa;, instead of separating,. 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed. and tr. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
