. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. DEVELOPMENT. 213 in number) with scalloped edges. Next, the pile breaks up into separate segments, which are, in fact, so many dis- tinct animals; and each turning over as it is set free, so as to bring the mouth below, develops into an adult Me- dusa, becoming more and more convex, and furnished with tentacles, circular canals, and other organs exactly like those of the progenitor that laid the original egg. Here we see a Medusa producing eggs which devel
. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. DEVELOPMENT. 213 in number) with scalloped edges. Next, the pile breaks up into separate segments, which are, in fact, so many dis- tinct animals; and each turning over as it is set free, so as to bring the mouth below, develops into an adult Me- dusa, becoming more and more convex, and furnished with tentacles, circular canals, and other organs exactly like those of the progenitor that laid the original egg. Here we see a Medusa producing eggs which develop into stationary forms resembling Hydras. The Hydras. Fig. 178.—Alternate Generation: a, b, c, ova of an Acaleph (Chrysaora); d,e,f, Hy- dras ; g, h, Hydras with constrictions; i, Hydra undergoing fission; k, one of the separated segments, a free Medusa. then produce not only Medusae by budding in the manner described, but also other Hydras like themselves by bud- ding. All these intermediate forms are transient states of the Jelly-fish, but the metamorphoses cannot be said to occur in the same individual. While a Caterpillar becomes a Butterfly, this Hydra-like individual produces a number of Medusae. Alternate generation is, then, an alternation of asexual and sexual methods of reproduction, one or more generations produced from buds being followed by a single generation produced from eggs. Often, as in the fresh-water Hydra, the two kinds of generations are alike in appearance. The process is as wide spread as asexual reproduction, being found mostly in Sponges, Coelenterates, and Worms. It is also found in certain. 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 Orton, James, 1830-1877; Birge, E. A. (Edward Asahel), 1851-1950. New York : Harper & Bros.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1883
