The cell in development and inheritance . nerating tissues after irritative stimulus (Strobe);but it is uncertain whether such mitoses lead to the formation ofnormal tissue.^ The frequency of abnormal mitoses in pathological growths is amost suggestive fact, but it is still wholly undetermined whether theabnormal mode of cell-division is the cause of the disease or thereverse. The latter seems the more probable alternative, since nor-mal mitosis is certainly the rule in abnormal growths ; and Galeottisexperiments suggest that the pathological mitoses in such growthsmay be caused by the presenc
The cell in development and inheritance . nerating tissues after irritative stimulus (Strobe);but it is uncertain whether such mitoses lead to the formation ofnormal tissue.^ The frequency of abnormal mitoses in pathological growths is amost suggestive fact, but it is still wholly undetermined whether theabnormal mode of cell-division is the cause of the disease or thereverse. The latter seems the more probable alternative, since nor-mal mitosis is certainly the rule in abnormal growths ; and Galeottisexperiments suggest that the pathological mitoses in such growthsmay be caused by the presence of deleterious chemical products inthe diseased tissue, and perhaps point the way to their medicaltreatment. ^ The remarkable polyasters formed in polyspermic fertilization of the egg are de-scribed at page 198. lOO CELL-DIVISION D. The Mechanism of Mitosis We now pass to a consideration of the forces at work in mitoticdivision, which leads us into one of the most debatable fields of cytological inquiry. I. Function of the AmpJii-aster. ac Fig. 48. — Slightly schematic figures of dividing eggsof Ascaris, illustrating Van Benedens theory of mitosis.[Van Beneden and Julin.] A. Early anaphase; each chromosome has dividedinto two. B. Later anaphase during divergence of thedaughter-chromosomes, Antipodal cone of astralrays ; cortical zone of the attraction-sphere ; i. inter-zonal fibres stretching between the daughter-chromo-somes ; medullary zone of the attraction-sphere; principal cone, forming one-half of the contractilespindle (the action of these fibres is reenforced by that ofthe antipodal cone) ; subequatorial circle, to whichthe astral rays are attached. All observers agree thatthe amphiaster is in somemanner an expression ofthe forces by which cell-division is caused, andmany accept, in one formor another, the first viewclearly stated by Fol,^ thatthe asters represent insome manner centres ofattractive forces focussedin the centrosome
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