ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 935 



In regard to tlie theory of heredity, Dr. Weismann concludes that the 

 germinal cells of a single individual do not embody similar hereditary 

 tendencies, but that in this relation they are all different, and that no two 

 provide quite the same combination of tendencies. This he thinks explains 

 the long-recognized differences between the children of the same father and 

 mother ; and he adds that the deeper import of this arrangement must be 

 seen in freely-conditioned ever-newly-blending individual variability, for 

 sexual reproduction appears more and more in the light of an arrange- 

 ment by which an ever-changing wealth of individual conformations is 

 handed on. 



B. Histology.* 



Theory of Cell-division.j — Herr G. Platner has been led by the results 

 of his study of karyokinesis in Lepidoptera to seek to lay the foundations 

 at least of a theory of cell-division. He has tackled the problem of 

 cellular mechanics, and finds the condition of nuclear division to be in part 

 at least streaming of the protoplasm, such as is familiar in pseudopodia 

 and Myxomycetes. The phenomena of karyokinesis can be explained as the 

 results either (1) of chemical processes influencing the cellular substance, 

 or (2) of protoplasmic movements due to the above or to external influences, 

 or (3) of unknown molecular and attractive forces. 



According to Platner, the separation of the daughter elements on the 

 dislocation of the equatorial plate (Flemming's metakinesis) is the result 

 of a circulating stream. The form and position of the nuclear spindle 

 are mechanically conditioned by fluid movements within the latter, and 

 radiating from tlae poles. The appearance of the primary asters depends 

 upon the direction in which the stream of nutritive fluid circulates through 

 the cell, and the spindle developes at right angles to this. The same causes 

 efiiect the movements of the nucleus. The formation of the nuclear coil, 

 and the disposition of the equatorial plate is the result of plasmic streams 

 penetrating the nucleus in given direction. The achromatic substance is 

 the active element in karyokinesis. The division of the protoplasm is a 

 purely mechanical process. 



Synthetic Processes in Living Cells.| — Fniulein J. Brinck and Herr 

 H. Kronecker submit the results of numerous observations on the physio- 

 logical relations between living cells and various substances. Their ex- 

 periments led to the following conclusions: — (1) Serum-albumin is more 

 surely characterized by its nutritive relation to muscle, than by physical 

 and chemical reactions ; (2) stomachic peptones are still albuminoids in 

 the physiological sense, pancreatic peptones are not; (3) Stomachic 

 peptones are reconverted into serum-albumin by many kinds of living 

 cells ; (4) a bacillus has the same useful property of forming serum-albumin 

 from stomachic peptones ; (5) pathogenic bacilli have a destructive influence. 



Structure and Distribution of Striped and Unstriped Muscle in the 

 Animal Kingdom.§ — Mr. C. F. Marshall has endeavoured to trace the 

 distribution of the intracellular network of the strij)ed muscle-fibre in the 

 animal kingdom. It is pointed out that the striation of muscle must not be 

 confounded with the transversely striated ajjpearance which is caused by 

 the corrugation of the outline of the fibre, and which is probably due to a 

 state of over-contraction. 



* This section is limited to papers relating to Cells and Fibres. 

 + Intemat. Monatschrift f. Anat. u. HistoL, iii. (1886) p. 10. Naturforscher, xx 

 (1887) p. 315. 



X Arehiv. f. Anat. u. Physiol., 1887, pp. 347-9. 



§ Quart. Joum. Micr. Sci., xxviii. (1887) pp. 75-107 (1 pi.). 



