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actinian adult americanus animal Anopheles appear body brood buff Bufo castrated ccelomic cent cestode chromatin chromosomes cleavage cocoons colony color corpuscles Culex cyprinids cyst cytoplasm determined division dorsal ectoderm eggs embryo endoderm evidence Explanat1on of Plate feathers fertilized figures filaments fish formation frog germ cells growth haematoxylin hatched head heterochromosomes individuals iron haematoxylin laceration piece large number larvae latipes Leptinotarsa male membrane mesenteries Microstoma mitosis Moniezia muscle mussels Necturus nematocysts nest normal nuclei nucleolus observed obtained occur oogonia ovary pair parasite parenchyma percentage of females polarity primary anlage proglottids pupae queens killed region salamander scales second zooid seen series of experiments sex ratios shown in Fig side solution species specimens sperm spermatocyte spermatogonia spermatozoa spiders stage staining stomodeum surface tadpoles tentacles tissue uterus vacuole ventral vitellarium workers worm yolk young zooid Zool
Page 191 - ... during the latter part of June and the early part of July, but leaves the latter part of the summer poorly occupied.
Page 74 - ... reacts positively to large patches of bright sunlight rather than to small ones, even though the latter, as in the case of the sun, may be much more intense." Cole2 has confirmed Parker's results, and concluded from his own painstaking observations on several forms, that animals with direction eyes, as those without eyes, respond to light intensity only; and that animals with image-forming eyes when positively 1"The Phototropism of the Mourning Cloak Butterfly, Vanessa antiopa Linn.,
Page 367 - I did both eagerly, and acquired a considerable knowledge of the literature of ichthyology, becoming especially interested in the system of classification, then most imperfect. I tried to follow Agassiz's scheme of division into the order of ctenoids and ganoids, with the result that I found one of my species of side-swimmers had cycloid scales on one side and ctenoid on the other. This not only shocked my sense of the value of classification in a way that permitted of no full recovery of my original...
Page 367 - ... learned the art of comparing objects, which is the basis of the naturalist's work. At this stage I was allowed to read and to discuss my work with others about me. I did both eagerly, and acquired a considerable knowledge of the literature of ichthyology, becoming especially interested in the system of classification, then most imperfect. I tried to follow Agassiz's scheme of division into the order of ctenoids and ganoids, with the result that I found one of my species of side-swimmers had cycloid...
Page 163 - A revision of the adult cestodes of cattle, sheep and allied animals by CW Stiles and Albert Hassall.
Page 124 - ... this; for in spite of extensive investigation, we still have no very definite conclusion in regard either to the mechanism of amitosis or its biological meaning. Amitosis, or direct division, differs in two essential respects from mitosis. First, the nucleus remains in the resting state (reticulum), and there is no formation of a spireme or of chromosomes. Second, division occurs without the formation of an amphiaster ; hence the centrosome is not concerned with the nuclear division, which takes...
Page 162 - Gough ["A Monograph of the Tapeworm of the Subfamily Avitellininae. being a revision of the Genus Stilesia, and an account of the Histology of Avitellina centripunctata (Riv...
Page 80 - Isely so aptly remarks (1911, p. 79) " This kind of environment gives a constant supply of oxygen and sufficient food ; is free from shifting sand and silt accumulation. Those mussels that drop from the fish in these favorable situations develop in large numbers, while the less fortunate, that drop in shifting sand and silt, die early.
Page 233 - ... capable of giving sex to the resulting embryo; but in many forms besides the bee the spermatozoan may be a sex-changing factor if not a sex-determining one. LITERATURE CITED. Aristotle. '62 History of Animals. Translated by R. Cresswell. Published by Henry Bohn, London.