192 THOMAS H. r.HYCR. 



three grades of asters are formed — primary, secondary, and 

 tertiary. The last contribute to the secondary, and these 

 again to the primary or definitive asters. Carnoy described 

 accessory asters during the formation of the second polar 

 body in Ascaris, and Meade (1897) showed that a great 

 number of such asters were formed before the formation of 

 the first polar spindle in Chtetopterus (an Annelid), which he 

 thought contributed to the formation of the spindle asters. 

 Watase (in Macrobdella) found as many as thirteen asters in 

 the cytoplasm, with centres varying in size from the smallest 

 microsome to the true centrosome. Griffin (1899) also de- 

 scribes the formation of accessory asters in Thalassema. 

 These experiments and observations ai'e held to afford strong 

 evidence of the free formation of the centrosome, in which 

 case both that body and its aster would be the expression 

 rather than the cause of cell activities. 



The secondary asters in Echinus at this stage are pos- 

 sibly produced in the cytoplasm under the influence of the 

 nuclear material let loose on the disappearance of the nuclear 

 membrane. 



All this tallies better with Strasburger's views of the kino- 

 plasm than with any other theory. He thinks of protoplasm 

 as of two kinds, trophoplasm and kinoplasm : the former is 

 vegetative in function and alveolar in structure ; the latter 

 presides over the activities of the cell, forms centrosomes, 

 mid-bodies, asters, and spindles, constitutes a peripheral layer 

 from which membranes and cilia are derived, and is fibrillar 

 in structure. '^IMiis differentiation of the pi'otoplasm takes 

 place when mitosis sets in. Further, ho thinks the nucleolus 

 is a storehouse of reserve material, out of which, on need, the 

 substance of the kinoplasm is drawn. 



I have shown that the nucleolus at first seems to contain 

 all the chromatin substance which later is found in the 

 nuclear reticulum, the larger portion of which is rejected, to 

 form in turn, if I bo right, directly or indirect)}' a 

 reticular zone, out of which the asters and spindle are 

 spun. 



