. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. CrXIlRATIVE 373 in front of the last segment of the asexual form, and these segments, after the formation of a head, constitute a new individual. As this process is repeated, a chain of connected individuals is formed, and these, as soon as they are separated, represent the sexual individuals. Among the freshwater Naidce, in Chcetogaster, a regular and continued budding in the long axis leads to the formation of chains, consisting of not less than 12 to 16 zooids, each having only four segm
. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. CrXIlRATIVE 373 in front of the last segment of the asexual form, and these segments, after the formation of a head, constitute a new individual. As this process is repeated, a chain of connected individuals is formed, and these, as soon as they are separated, represent the sexual individuals. Among the freshwater Naidce, in Chcetogaster, a regular and continued budding in the long axis leads to the formation of chains, consisting of not less than 12 to 16 zooids, each having only four segments, whDe the sexual individuals consist of a greater number of segments. A similar process occurs in the mode of reproduction observed by O. Fr. Miiller in Xais jjrohoscidea, from the last segment of which a new zooid is produced. Both generations of Nais, however^ become sexually mature. [For a more complete account of the asexual reproduction of Ch;ctopoda, ride Balfour, "Comparative Embryology," vol. i., pp. 283, 28-t.] The Glicetopoda are, with the exception of the her- maphrodite OligochcBta and certain Serpididce {, Sjn- rorhis S2nrillum, Protula Dysteri) of separate sexes. Male and female individuals seem occasionally so stiikingly different in the structure of Fig. 303.—a parapodium of TomopterU with a their organs of sense and lo- ™^^^ °* "^'^ ^""^ °°^ *^^e o^""^ (^"e'- C- ° Gegenbaur). comotion that they have even been taken for species of distinct genera. Besides the above- mentioned Sacconereis and Polyhostrichus, the asexual generation of which is Autolyt'ios, a similar sexual dimorphism has been shown by Malmgren for Heteronereis, a genus of the Lycoridce, in which the males and females differ both in external form and in the number of their segments. A remarkable case of heterogamy is also afforded by this genus, in that a generation of smaller animals swimming iipon the surface alternates with a generation of
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanimals, bookyear1892
