The American Naturalist, Volumen30Essex Institute, 1896 |
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Página 1
... known , and yet is an es- sential link in the chain of reasoning , I venture to repeat it- Though written in 1885 , I consider that to - day it is still suffi- cient to disprove Weismann's theory of germ plasm . Weis- mann has not ...
... known , and yet is an es- sential link in the chain of reasoning , I venture to repeat it- Though written in 1885 , I consider that to - day it is still suffi- cient to disprove Weismann's theory of germ plasm . Weis- mann has not ...
Página 23
... known conditions from seeds in the same manner as the petu- nias were , which I have mentioned . The plants varied widely . Seeds of these plants were saved and all sown in one soil , and the characters , somewhat diminished , appeared ...
... known conditions from seeds in the same manner as the petu- nias were , which I have mentioned . The plants varied widely . Seeds of these plants were saved and all sown in one soil , and the characters , somewhat diminished , appeared ...
Página 54
... known . From his observations the writer infers that the colonial stock was carried by a large air bladder , to the underside of which was attached the funicle . The latter was enclosed in the central disc , and this was surrounded by a ...
... known . From his observations the writer infers that the colonial stock was carried by a large air bladder , to the underside of which was attached the funicle . The latter was enclosed in the central disc , and this was surrounded by a ...
Página 64
... known which can be induced to form this or that sporangium , or none at all , by means of purely external , known conditions . He believes the production of the first type is due to substrata in which nitrogen- ous substances ...
... known which can be induced to form this or that sporangium , or none at all , by means of purely external , known conditions . He believes the production of the first type is due to substrata in which nitrogen- ous substances ...
Página 114
... known from only four widely separated localities ; one of these , that of Black Butte , Wyoming , is west of the main range of the Rocky Mountains , and the other three including the Denver locality in Colorado ; the Converse Co ...
... known from only four widely separated localities ; one of these , that of Black Butte , Wyoming , is west of the main range of the Rocky Mountains , and the other three including the Denver locality in Colorado ; the Converse Co ...
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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...