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achromatic albumin alveolar amphiaster anaphase Anat animals annelids Arch arise Ascaris asters astral rays attraction-sphere axial filament Befruchtung Beneden Biitschli blastomeres Boveri cell-body cell-division cells central granule central spindle centre centrosome centrosphere chemical chromatin chromatin-granules chromosomes cleavage conclusion conjugation containing cytoplasm daughter-cells daughter-chromosomes definite degenerate described deutoplasm differentiation divide division Driesch early echinoderms egg-nucleus embryo fact fertilization fibres fibrillar Flemming formation germ-cells germ-nuclei germinal vesicle give rise growth Heidenhain Hertwig hypothesis Ibid idioplasm iiber Kostanecki large number longitudinal macronucleus mass maturation-divisions membrane Meves microsomes middle-piece mitosis mitotic figure morphological nucleinic acid nucleoli nucleus number of chromosomes observers organization origin ovum physiological plants plastids polar bodies polar spindle pole prophase protoplasm reduction regarded relation result Riickert salamander sea-urchin segments showing shown somatic sperm-aster sperm-nucleus spermatids spermatocytes spermatozoon sphere spindle-fibres spireme split staining Strasburger structure tetrads theory tion true nucleoli Uber Weismann yolk-nucleus
Page 13 - The child inherits from the parent germ cell, not from the parent body, and the serin cell owes its characteristics not to the body which bears it but to its descent from a preexisting germ cell of the same kind. Thus the body is as it were an offshoot from the germ cell. As far as inheritance is concerned the body is merely the carrier of the germ cells which are held in trust for coming generations.
Page 362 - ... of cell-division, first formulated by Sachs in the case of plantcells. These are : 1. The cell typically tends to divide into equal parts. 2. Each new plane of division tends to intersect the preceding plane at a right angle. In the simplest and least modified forms the direction of the cleavage-planes, and hence the general configuration of the cellsystem, depends on the general form of the dividing mass; for, as Sachs has shown, the cleavage-planes tend to be either vertical to the surface...
Page 433 - The idioplasm of every species has been derived, as we must believe, by the modification of a preexisting idioplasm through variation, and the survival of the fittest. Whether these variations first arise in the idioplasm of the germ-cells, as Weismann maintains, or whether they may arise in the body-cells and then be reflected back upon the idioplasm, is a question to which the study of the cell has thus far given no certain answer. Whatever position we take on this question, the same difficulty...
Page xi - PREFACE TO THE SECOND EDITION SINCE the appearance of the first edition of this work, in 1896, the aspect of some of the most important questions with which it...
Page 290 - Altmann, that the protoplasmic granules might be actually organic units or bioblasts, capable of assimilation, growth, and division, and hence to be regarded as elementary units of structure standing between the cell and the ultimate molecules of living matter.
Page 67 - The remarkable fact has now been established with high probability that every species of plant or animal has a fixed and characteristic number of chromosomes, which regularly recurs in the division of all of its cells ; and in all forms arising by sexual reproduction the number is even.
Page 488 - Cloth, $1.50 net. This work has been prepared to meet the needs of the nurse, both in the training school and after graduation. It aims to give the essentials of dietetics, considering briefly the physiology of digestion and the various classes of foods and the part they play in nutrition. American Journal of Nursing...
Page 22 - For these and other reasons the terms "nucleus" and "cell-body" should probably be regarded as only topographical expressions denoting two differentiated areas in a common structural basis. The terms karyoplasm and cytoplasm possess, however, a specific significance owing to the fact that there is on, the whole a definite chemical contrast between the nuclear substance and that of the cell-body, the former being characterized by the abundance of a substance rich in phosphorus known as...
Page 1 - 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 121 - The effect of mitosis is to produce a meristic division, as opposed to a mere massdivision, of the chromatin of the mother-cell, and its equal distribution to the nuclei of the daughter-cells. To this result all the operations of mitosis are tributary ; and it is a significant fact that this process is characteristic of all embryonic and actively growing cells, while mass-division, as shown in amitosis, is equally characteristic of highly specialized or degenerating cells in which development is...