Life Histories of Animals, Including Man: Or, Outlines of Comparative EmbryologyH. Holt, 1876 - 243 páginas |
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Life Histories of Animals, Including Man: Or, Outlines of Comparative Embryology Alpheus Spring Packard Visualização completa - 1876 |
Life Histories of Animals, Including Man: Or, Outlines of Comparative Embryology Alpheus Spring Packard Visualização completa - 1876 |
Life Histories of Animals, Including Man: Or, Outlines of Comparative Embryology Alpheus Spring Packard Visualização completa - 1876 |
Termos e frases comuns
abdomen adult form Agassiz alimentary canal allantois amnion Amoeba Amphioxus animals Annelides antennæ appear appendages arise ascidians Balanoglossus becomes begins Beneden blastoderm body cavity Brachiopods budding capsule cells Cercaria Cienkowski ciliated Claparède Clark crabs Crustacea cyst digestive cavity disk dorsal Echinoderms ectoderm elongates embryo embryology encysted endoderm Entwickelung Entwickelungsgeschichte fishes flagellum gastrula germ germinal gills Gregarina Hæckel hatching head Hydra Hydroids Infusoria inner insects intestine Kölliker's Zeitschrift Kowalevsky Lacaze-Duthiers larva larvæ layer leaves the egg life-history Lovén mass maxillæ membrane metamorphosis Metschnikoff mode of development mode of growth mollusks monads Moner Morula moult mouth Müller Nauplius nucleus observed organs outer germ-layer oval ovary pairs partial pass planula polypes polypide Polyzoa primitive band protoplasm Radiolaria represents reproductive Salensky seen shell side Siebold and Kölliker's soon species sponge stage starfish stomach tail tentacles tube Ueber undergoes total segmentation Veliger velum vertebrates worms yolk young zoospores
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Página 15 - Leidy describes 2 a form which he thinks "is probably a member of the genus Pelomyxa," and which is characterized by the comparatively enormous quantity of quartzose sand which it swallows with its food. " The animal might be viewed as a bag of sand !" It is from one-eighth to three-eighths of a line in diameter, and was found on the muddy bottom of ponds in Pennsylvania and New Jersey. It is possibly Pamphagus mutabilis, figured by Professor Bailey in the "American Journal of Science and Arts,
Página 35 - When fully expanded they appear round, as at cv; but when contracted they appear, observes Clark, as "fine radiating streaks, and as the main portion lessens they gradually broaden and swell unt.il the former is emptied and nearly invisible, and they are extended over half the length of the body. In this condition they might be compared to the arterial vessels of the more elevated classes of animals, but they would at the same time represent the veins, since they serve at the next moment to return...
Página 120 - Anatomy," with the addition of the Brachiopoda, which he still retains among the Mollusca. The Onychophora, represented by Peripatus, are also omitted, as since the publication of Gegenbaur's work, Peripatus has been proved by the researches of Mr. Moseley to be a tracheate insect, for in the young genuine tracheae exist, though they disappear in the adult, or at least have not been discovered.
Página 227 - The heart originates also in the head-fold at about the time the protovertebrae are formed, and the rudiment is situated below the fore gut or rudiment of the alimentary canal; by the end of the first half of the second day it is flask-shaped, with a slight bend to the right. " Soon after its formation the heart begins to beat, its at first slow and rare pulsations beginning at the venous and passing on to the arterial end.
Página 97 - In this stage the larval oyster leaves the mother and swims around in the water, the cilia of the velum keeping up a lively rotary motion. In this state Lacaze-Duthiers observed it for forty-three days, without any striking change in form, except that the velum increased in size, and the auditory vesicle appeared, containing several otoliths, which kept up a rapid motion. But still the gills and heart were wanting. Of its further history we know but little, except that it becomes fastened to some...
Página 15 - Imagine an animal, like one of our autumnal spiders stationed at the centre of its well-spread net ; imagine every thread of this net to be a living extension of the animal, elongating, branching, and becoming confluent so as to form a most intricate net; and imagine every thread to exhibit actively moving currents of a viscid liquid both outward and inward, carrying along particles of food and dirt, and you have some idea of the general character of a Gromia.
Página 174 - ... sea water in which the embryo revolves. At a little later period the embryo throws off an embryonal skin, the thin pellicle floating about in the egg. Still later in the life of the embryo the claws are developed, an additional rudimentary gill appears, and the abdomen grows broader and larger, with the segments more distinct ; the heart also appears, being a pale streak along the middle of the back extending from the front edge of the head to the base of the abdomen.
Página 42 - The smaller vescicle he regards as the germinal vesicle, and the larger as the vitelline membrane. After the fecundation, "at the end of four or five days, the development of the eggs is complete, and each, with the aid of reagents, displays in a very distinct manner its characteristic elements, namely, vitelline membrane, vitellus, germ-vesicle and germ-spot.
Página 26 - Chilodon has a complete circle of straight rods around the mouth. As for the pivot it is nothing but a kind of stem, such as exists on a larger scale in Stentor, or is more particularly specialized in the pedestals of Epistylis, Zoothamnium, or Podophrya ; and as counter to what we see in these last, I would state that there are certain of the Vorticellians closely related to Epistylis, which have no stem whatever, and swim about as freely as Dysteria.
Página 66 - The second set of Hydras differ only from the "feeders" in having shorter tentacles twisted like a corkscrew. In the third and last set of Hydras the mouth is closed, and they differ from the others in having a single tentacle instead of a cluster. Their function has not yet been clearly explained. Gradually new individuals are added, until a long chain of Hydroids is formed, which move gracefully through the water, with the oil globule uppermost, which serves as a float and is identical with the...