The American Naturalist, Volumen30Essex Institute, 1896 |
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Página 22
... seen ; and most fungi , which have run into numberless forms , are sexless . In the third place , since all agree that plants are intimately adapted to the conditions in which they live , it is violence to suppose that the very ...
... seen ; and most fungi , which have run into numberless forms , are sexless . In the third place , since all agree that plants are intimately adapted to the conditions in which they live , it is violence to suppose that the very ...
Página 27
... seen . Fig . 3 represents diagrammatically the appearance of the retina after the front of the eye has been removed . In order to show the angles which the lines of vision make with the median plane , sections were made through the ...
... seen . Fig . 3 represents diagrammatically the appearance of the retina after the front of the eye has been removed . In order to show the angles which the lines of vision make with the median plane , sections were made through the ...
Página 29
... seen if it be present , but the area is some- times very difficult to discern , and , were it not for the blood- vessels acting as land - marks , it might be overlooked altogether . Drawings were made of this posterior half , great care ...
... seen if it be present , but the area is some- times very difficult to discern , and , were it not for the blood- vessels acting as land - marks , it might be overlooked altogether . Drawings were made of this posterior half , great care ...
Página 30
... seen , so far as experiments have gone , that in mammals the presence of a fovea is the ex- ception while an area is the rule . The primates are the only mammals in which a fovea has been found . Most of the mam- mals examined have a ...
... seen , so far as experiments have gone , that in mammals the presence of a fovea is the ex- ception while an area is the rule . The primates are the only mammals in which a fovea has been found . Most of the mam- mals examined have a ...
Página 31
... seen , and the fovea is only seldom observed . The area centralis varies greatly in form and extent in dif- ferent animals . It varies from the round form of small extent found in the cat and the weasel to the band - like form found in ...
... seen , and the fovea is only seldom observed . The area centralis varies greatly in form and extent in dif- ferent animals . It varies from the round form of small extent found in the cat and the weasel to the band - like form found in ...
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acid adaptations Amer American animals appear augite bacteria beds beets birds body bones Botany brain Bull cells characters color containing Cope described diabases Diplopoda disease eggs embryo Eocene evidence evolution experiments Extr fact fauna fishes formation fossil gabbro gastrula gelatine genera genus Geol Geological gneisses heredity hornblende Hyracotherium insects known Lacertilia larvæ latter legs length less limestone mass ment method mineral molars movements Museum mushroom bodies natural NATURALIST North observed occur organism original orthoclase ovum Paleontology paper paroccipital phenocrysts plagioclase plants plates porphyritic premolar present probably Prof Professor protoplasm quartz recent region relation rocks Science segment selection side skull species specimens spores sporophylls squamosal stage stain stem structure subspecies substance surface tail tion tissues University upper variations vegetative
Pasajes populares
Página 911 - Its power of inducing fermentation in a solution of sugar was entirely destroyed, although no perceptible change in the appearance of the yeast cells could be detected under the microscope. This experiment was repeated several times, and always with the same result, although when the yeast was simply washed in water it readily induced fermentation.
Página 189 - Consequently, if the theory be true, it is indisputable that before the lowest Cambrian stratum was deposited, long periods elapsed, as long as, or probably far longer than, the whole interval from the Cambrian age to the present day; and that during these vast periods the world swarmed with living creatures.
Página 552 - Does the organism learn to make new adjustments, or to modify old ones, in accordance with the results of its own individual experience? If it does so, the fact cannot be due merely to reflex action in the sense above described, for it is impossible that heredity can have provided in advance for innovations upon, or alterations of, its machinery during the lifetime of a particular individual.
Página 431 - Their houses are mats or barks of trees, set on poles in the fashion of an English barn, but out of the power of the winds, for they are hardly higher than a man.
Página 169 - Illustrations of the dynamic metamorphism of anorthosites and related rocks in the Adirondacks...
Página 862 - Assistant Secretary of the Smithsonian Institution and Director of the National Museum, died in Washington, Sept.
Página 409 - Triarthrus. No traces of any special organs for this purpose have been found in this genus, and their former existence is very doubtful, especially in view of the perfection of details preserved in various parts of the animal. The delicacy of the appendages and ventral membrane of trilobites and their rarity of preservation are sufficient demonstration that these portions of the outer integument were of extreme thinness, and therefore perfectly capable of performing the function of respiration. Similar...
Página 544 - Naturalist. [July, ments) — but by the reinstatement of it by a discharge of the energies of the organism, concentrated as far as may be for the excessive stimulation of the organs (muscles, etc.) most nearly fitted by former habit to get this stimulation again (in which the " stimulation " stands for the condition favorable to adaptation).
Página 994 - We must therefore picture to ourselves a fertile plain occupying the whole of the Bristol Channel, and supporting herds of reindeer, horses, and bisons, many elephants and rhinoceroses, and now and then being traversed by a stray hippopotamus, which would afford abundant prey to the lions, bears, and hyaenas, inhabiting all the accessible caves, as well as to their great enemy and destroyer, man."* III.
Página 940 - In reviewing the results of these investigations and comparing one species with another, without losing sight of the fact that comparative good is not necessarily positive good, it appears that of 7 species considered the Downy Woodpecker is the most beneficial. This is due in part to the great number of insects it eats and in part to the nature of its vegetable food, which is of little value to man. Three-fourths of its food consists of insects, and few of these are useful kinds. Of grain, it eats...