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abdomen alimentary canal Ameba Anatomy animals antenna appendages basal become blood body wall cavity Ccelenterates ccelom Cell Division chemical chitinous chromosomes cilia cleavage colony conjugation consists containing contractile crayfish cuticle cytoplasm digestive divides dorsal drone earthworm ectoderm embryology Euglena excretory external female fertilized fibers functions gametes germ cells germ layers glands hive honey honeybee Hydra individuals insects intestine Journ known large number larvae layer living longitudinal male mature membrane Metazoa micronucleus mitosis mouth muscles nematocysts nerve cord nervous system nucleus ovary pair Paramecia Paramecium parasite particles pass phylum Planaria pollen pollen basket polyp posterior end present produced protoplasm Protozoa queen reaction Regeneration region segments side somite species sperm spermatocytes spermatozoa stages statocyst stimuli structure substance surface swim tentacles theory Thigmotropism thorax tion tissue Triploblastic tube usually vacuole ventral vessel Volvox walking legs worker worm Zoology zygote
Page 262 - Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the number of cats that destroy the mice." Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!
Page 285 - Given any species in any region, the nearest related species is not likely to be found in the same region nor in a remote region, but in a neighboring district separated from the first by a barrier of some sort, or at least by a belt of country, the breadth of which gives the effect of a barrier.
Page 303 - INSTINCT is usually defined as the faculty of acting in such a way as to produce certain ends, without foresight of the ends, and without previous education in the performance.
Page 262 - Hence we may infer as highly probable that, if the whole genus of humble-bees became extinct, or very rare, in England, the heartsease and red clover would become very rare or wholly disappear.
Page 306 - We know not where consciousness begins in the animal world. We know where it surely resides — in ourselves; we know where it exists beyond a reasonable doubt — in those animals of structure resembling ours which rapidly adapt themselves to the lessons of experience. Beyond this point, for all we know, it may exist in simpler and simpler forms until we reach the very lowest of living beings.
Page 262 - I have also found that the visits of bees are necessary for the fertilization of some kinds of clover; for instance, twenty heads of Dutch clover (Trifolium repens) yielded 2,290 seeds, but twenty other heads, protected from bees, produced not one.
Page 35 - DURING the half-century that has elapsed since the enunciation of the cell-theory by Schleiden and Schwann, in 1838-39, it has become ever more clearly apparent that the key to all ultimate biological problems must, in the last analysis, be sought in the cell.
Page 36 - No other biological generalization, save only the theory of organic evolution, has brought so many apparently diverse phenomena under a common point of view or has accomplished more for the unification of knowledge.
Page 301 - The fittest are thus the most sociable animals, and sociability appears as the chief factor of evolution, both directly, by securing the well-being of the species while diminishing the waste of energy, and indirectly, by favouring the growth of intelligence.
Page 354 - By KARL A. VON ZITTEL, Professor of Geology and Palaeontology in the University of Munich. Translated and edited by CHARLES R. EASTMAN, Ph.D., in charge of Vertebrate Palaeontology in the Museum of Comparative Zoology at Harvard College, Cambridge, Mass.